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Information on EC 2.7.7.72 - CCA tRNA nucleotidyltransferase
for references in articles please use BRENDA:EC2.7.7.72
Word Map on EC 2.7.7.72
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The expected taxonomic range for this enzyme is: Bacteria, Eukaryota, Archaea
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EC NUMBER 
COMMENTARY 
2.7.7.72
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RECOMMENDED NAME
GeneOntology No.
CCA tRNA nucleotidyltransferase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT
LITERATURE
a tRNA precursor + CTP = a tRNA with a 3' cytidine end + diphosphate
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a tRNA with a 3' CC end + ATP = a tRNA with a 3' CCA end + diphosphate
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a tRNA with a 3' cytidine + CTP = a tRNA with a 3' CC end + diphosphate
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a tRNA precursor + 2 CTP + ATP = a tRNA with a 3' CCA end + 3 diphosphate
overall reaction
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a tRNA precursor + 2 CTP + ATP = a tRNA with a 3' CCA end + 3 diphosphate
catalytic core and reaction mechanism of class I CCA-adding enzymes, overview
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a tRNA precursor + 2 CTP + ATP = a tRNA with a 3' CCA end + 3 diphosphate
catalytic core and reaction mechanism of class II CCA-adding enzymes, overview
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a tRNA precursor + 2 CTP + ATP = a tRNA with a 3' CCA end + 3 diphosphate
catalytic core and reaction mechanism of class II CCA-adding enzymes, overview
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a tRNA precursor + 2 CTP + ATP = a tRNA with a 3' CCA end + 3 diphosphate
catalytic core and reaction mechanism of class I CCA-adding enzymes, overview
-
a tRNA precursor + 2 CTP + ATP = a tRNA with a 3' CCA end + 3 diphosphate
catalytic core and reaction mechanism of class II CCA-adding enzymes, overview
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a tRNA precursor + 2 CTP + ATP = a tRNA with a 3' CCA end + 3 diphosphate
catalytic core and reaction mechanism of class II CCA-adding enzymes, overview
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SYSTEMATIC NAME
IUBMB Comments
CTP,CTP,ATP:tRNA cytidylyl,cytidylyl,adenylyltransferase
The acylation of all tRNAs with an amino acid occurs at the terminal ribose of a 3' CCA sequence. The CCA sequence is added to the tRNA precursor by stepwise nucleotide addition performed by a single enzyme that is ubiquitous in all living organisms. Although the enzyme has the option of releasing the product after each addition, it prefers to stay bound to the product and proceed with the next addition [5].
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ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
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GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
evolution
malfunction
physiological function
additional information
evolution
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a class I CCA-adding enzyme. CCA-adding enzymes are essential RNA polymerases that emerged twice in evolution leading to different structural characteristics and unusual mechanistic solutions for an error-free and sequence-specific CCA polymerization reaction. The catalytic cleft is formed by the head, neck, and body domains. Evolution of class I and class II CCA-adding enzymes as well as poly(A) polymerases, overview
evolution
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CCA-adding enzymes are essential RNA polymerases that emerged twice in evolution leading to different structural characteristics and unusual mechanistic solutions for an error-free and sequence-specific CCA polymerization reaction. Evolution of class I and class II CCA-adding enzymes as well as poly(A) polymerases, overview
evolution
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a class II CCA-adding enzyme. Compared to class I, class II CCA-adding enzymes show a much higher evolutionary conservation of individual catalytic core motifs. Evolution of class I and class II CCA-adding enzymes as well as poly(A) polymerases, overview
evolution
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a class II CCA-adding enzyme. Compared to class I, class II CCA-adding enzymes show a much higher evolutionary conservation of individual catalytic core motifs. Evolution of class I and class II CCA-adding enzymes as well as poly(A) polymerases, overview
evolution
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a class I CCA-adding enzyme. CCA-adding enzymes are essential RNA polymerases that emerged twice in evolution leading to different structural characteristics and unusual mechanistic solutions for an error-free and sequence-specific CCA polymerization reaction. The catalytic cleft is formed by the head, neck, and body domains. Evolution of class I and class II CCA-adding enzymes as well as poly(A) polymerases, overview
evolution
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a class II CCA-adding enzyme. Compared to class I, class II CCA-adding enzymes show a much higher evolutionary conservation of individual catalytic core motifs. The templating motif carries the sequence DDxxR, a slight deviation from the usual EDxxR motif. Evolution of class I and class II CCA-adding enzymes as well as poly(A) polymerases, overview
evolution
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a class II CCA-adding enzyme. Compared to class I, class II CCA-adding enzymes show a much higher evolutionary conservation of individual catalytic core motifs. Evolution of class I and class II CCA-adding enzymes as well as poly(A) polymerases, overview
evolution
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with a possible origin of ancient telomerase-like activity, the CCA-adding enzymes obviously emerged twice during evolution, leading to structurally different, but functionally identical enzymes. While the enzyme class 1 is exclusively found in archaea, class 2 tRNA-nucleotidyltransferases are present in eukaryotes and bacteria. Class 1 enzymes have a tRNA-binding body domain consisting of a beta sheet with flanking alpha helices. Head and neck domains form the active site and are also composed of alpha-helical and beta-sheet elements. The chemical mechanism underlying the polymerization appears conserved in all polymerases across the three kingdoms of life
evolution
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with a possible origin of ancient telomerase-like activity, the CCA-adding enzymes obviously emerged twice during evolution, leading to structurally different, but functionally identical enzymes. While the enzyme class 1 is exclusively found in archaea, class 2 tRNA-nucleotidyltransferases are present in eukaryotes and bacteria. Class 1 enzymes have a tRNA-binding body domain consisting of a beta sheet with flanking alpha helices. Head and neck domains form the active site and are also composed of alpha-helical and beta-sheet elements. The chemical mechanism underlying the polymerization appears conserved in all polymerases across the three kingdoms of life
evolution
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with a possible origin of ancient telomerase-like activity, the CCA-adding enzymes obviously emerged twice during evolution, leading to structurally different, but functionally identical enzymes. While the enzyme class 1 is exclusively found in archaea, class 2 tRNA-nucleotidyltransferases are present in eukaryotes and bacteria. Class 1 enzymes have a tRNA-binding body domain consisting of a beta sheet with flanking alpha helices. Head and neck domains form the active site and are also composed of alpha-helical and beta-sheet elements. The chemical mechanism underlying the polymerization appears conserved in all polymerases across the three kingdoms of life
evolution
-
with a possible origin of ancient telomerase-like activity, the CCA-adding enzymes obviously emerged twice during evolution, leading to structurally different, but functionally identical enzymes. While the enzyme class 1 is exclusively found in archaea, class 2 tRNA-nucleotidyltransferases are present in eukaryotes and bacteria. Class 1 enzymes have a tRNA-binding body domain consisting of a beta sheet with flanking alpha helices. Head and neck domains form the active site and are also composed of alpha-helical and beta-sheet elements. The chemical mechanism underlying the polymerization appears conserved in all polymerases across the three kingdoms of life
evolution
-
with a possible origin of ancient telomerase-like activity, the CCA-adding enzymes obviously emerged twice during evolution, leading to structurally different, but functionally identical enzymes. While the enzyme class 1 is exclusively found in archaea, class 2 tRNA-nucleotidyltransferases are present in eukaryotes and bacteria. Class 1 enzymes have a tRNA-binding body domain consisting of a beta sheet with flanking alpha helices. Head and neck domains form the active site and are also composed of alpha-helical and beta-sheet elements. The chemical mechanism underlying the polymerization appears conserved in all polymerases across the three kingdoms of life
evolution
-
with a possible origin of ancient telomerase-like activity, the CCA-adding enzymes obviously emerged twice during evolution, leading to structurally different, but functionally identical enzymes. While the enzyme class 1 is exclusively found in archaea, class 2 tRNA-nucleotidyltransferases are present in eukaryotes and bacteria. In class 2 enzymes, only the head domain carries a beta sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure. The chemical mechanism underlying the polymerization appears conserved in all polymerases across the three kingdoms of life
evolution
-
with a possible origin of ancient telomerase-like activity, the CCA-adding enzymes obviously emerged twice during evolution, leading to structurally different, but functionally identical enzymes. While the enzyme class 1 is exclusively found in archaea, class 2 tRNA-nucleotidyltransferases are present in eukaryotes and bacteria. In class 2 enzymes, only the head domain carries a beta sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure. The chemical mechanism underlying the polymerization appears conserved in all polymerases across the three kingdoms of life
evolution
-
with a possible origin of ancient telomerase-like activity, the CCA-adding enzymes obviously emerged twice during evolution, leading to structurally different, but functionally identical enzymes. While the enzyme class 1 is exclusively found in archaea, class 2 tRNA-nucleotidyltransferases are present in eukaryotes and bacteria. Class 1 enzymes have a tRNA-binding body domain consisting of a beta sheet with flanking alpha helices. Head and neck domains form the active site and are also composed of alpha-helical and beta-sheet elements. The chemical mechanism underlying the polymerization appears conserved in all polymerases across the three kingdoms of life
evolution
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diphosphorolysis of class II enzymes establishes a fundamental difference from class I enzymes, and it is achieved only with the tRNA structure and with specific divalent metal ions
evolution
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diphosphorolysis of class II enzymes establishes a fundamental difference from class I enzymes, and it is achieved only with the tRNA structure and with specific divalent metal ions
evolution
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diphosphorolysis of class II enzymes establishes a fundamental difference from class I enzymes, and it is achieved only with the tRNA structure and with specific divalent metal ions
malfunction
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the enzyme knockout phenotype is a dramatic growth impairment, indicating the repair function of the CCA-adding enzyme on defective tRNAs lacking CCA ends due to hydrolytic damage
malfunction
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mutations around the active site of the Sulfolobus shibatae enzyme interfere with CCA-addition, but have only a minor affect on tRNA binding
malfunction
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mutations around the active site of the Sulfolobus shibatae enzyme interfere with CCA-addition, but have only a minor affect on tRNA binding
malfunction
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mutations around the active site of the Sulfolobus shibatae enzyme interfere with CCA-addition, but have only a minor affect on tRNA binding
malfunction
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mutations around the active site of the Sulfolobus shibatae enzyme interfere with CCA-addition, but have only a minor affect on tRNA binding
malfunction
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mutations around the active site of the Sulfolobus shibatae enzyme interfere with CCA-addition, but have only a minor affect on tRNA binding
malfunction
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CCA ends with misincorporated nucleotides are only rarely detected. Only under rather artificial in vitro conditions, e.g. in the presence of Mn2+ ions instead of Mg2+ or deviating NTP concentrations, incorporation of CCC as well as poly(C) tails can be observed
malfunction
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CCA ends with misincorporated nucleotides are only rarely detected. Only under rather artificial in vitro conditions, e.g. in the presence of Mn2+ ions instead of Mg2+ or deviating NTP concentrations, incorporation of CCC as well as poly(C) tails can be observed
malfunction
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CCA ends with misincorporated nucleotides are only rarely detected. Only under rather artificial in vitro conditions, e.g. in the presence of Mn2+ ions instead of Mg2+ or deviating NTP concentrations, incorporation of CCC as well as poly(C) tails can be observed
malfunction
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CCA ends with misincorporated nucleotides are only rarely detected. Only under rather artificial in vitro conditions, e.g. in the presence of Mn2+ ions instead of Mg2+ or deviating NTP concentrations, incorporation of CCC as well as poly(C) tails can be observed
malfunction
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CCA ends with misincorporated nucleotides are only rarely detected. Only under rather artificial in vitro conditions, e.g. in the presence of Mn2+ ions instead of Mg2+ or deviating NTP concentrations, incorporation of CCC as well as poly(C) tails can be observed
malfunction
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CCA ends with misincorporated nucleotides are only rarely detected. Only under rather artificial in vitro conditions, e.g. in the presence of Mn2+ ions instead of Mg2+ or deviating NTP concentrations, incorporation of CCC as well as poly(C) tails can be observed
malfunction
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CCA ends with misincorporated nucleotides are only rarely detected. Only under rather artificial in vitro conditions, e.g. in the presence of Mn2+ ions instead of Mg2+ or deviating NTP concentrations, incorporation of CCC as well as poly(C) tails can be observed
malfunction
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CCA ends with misincorporated nucleotides are only rarely detected. Only under rather artificial in vitro conditions, e.g. in the presence of Mn2+ ions instead of Mg2+ or deviating NTP concentrations, incorporation of CCC as well as poly(C) tails can be observed
physiological function
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all tRNA molecules carry the invariant sequence CCA at their 3'-terminus for amino acid attachment. The post-transcriptional addition of CCA is carried out by ATP(CTP):tRNA nucleotidyltransferase, also called CCase. This enzyme catalyses a unique template-independent but sequence-specific nucleotide polymerization reaction
physiological function
in all mature tRNAs, the 3'-terminal CCA sequence is synthesized or repaired by the template-independent nucleotidyltransferase ATP(CTP):tRNA nucleotidyltransferase. The phosphohydrolase activities of the HD domain of the tRNA nucleotidyltransferase are involved in the repair of the 3'-CCA end of tRNA, modeling, overview
physiological function
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CCA transferase participates in the maturation of tRNA lacking a CCA 3'-end
physiological function
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CCA-adding enzymes represent vital components of the cell's tRNA maturation and maintenance system. The CCA end, added to the tRNA by the CCA tRNA nucleotidyltransferase, is the site of aminoacylation, and aminoacyl tRNA synthetases fuse the individual amino acids to the ribose moiety of the terminal A residue. Second, the CCA terminus is required for the correct positioning of the aminoacyl-tRNA in the ribosome's A- and P-site in order to guarantee an efficient peptidyl transfer reaction. The CCA-adding enzyme represents an essential activity in the majority of organisms
physiological function
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CCA-adding enzymes represent vital components of the cell's tRNA maturation and maintenance system. The CCA end, added to the tRNA by the CCA tRNA nucleotidyltransferase, is the site of aminoacylation, and aminoacyl tRNA synthetases fuse the individual amino acids to the ribose moiety of the terminal A residue. Second, the CCA terminus is required for the correct positioning of the aminoacyl-tRNA in the ribosome's A- and P-site in order to guarantee an efficient peptidyl transfer reaction. The CCA-adding enzyme represents an essential activity in the majority of organisms, but in Escherichia coli, on the other hand, where CCA ends are encoded, this enzyme is dispensable, and a corresponding gene knockout is not lethal, but the repair function of the CCA-adding enzyme on defective tRNAs lacking CCA ends due to hydrolytic damage is required
physiological function
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CCA-adding enzymes represent vital components of the cell's tRNA maturation and maintenance system. The CCA end, added to the tRNA by the CCA tRNA nucleotidyltransferase, is the site of aminoacylation, and aminoacyl tRNA synthetases fuse the individual amino acids to the ribose moiety of the terminal A residue. Secondly, the CCA terminus is required for the correct positioning of the aminoacyl-tRNA in the ribosome's A- and P-site in order to guarantee an efficient peptidyl transfer reaction. The CCA-adding enzyme represents an essential activity in the majority of organisms
physiological function
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CCA-adding enzymes represent vital components of the cell's tRNA maturation and maintenance system. The CCA end, added to the tRNA by the CCA tRNA nucleotidyltransferase, is the site of aminoacylation, and aminoacyl tRNA synthetases fuse the individual amino acids to the ribose moiety of the terminal A residue. Secondly, the CCA terminus is required for the correct positioning of the aminoacyl-tRNA in the ribosome's A- and P-site in order to guarantee an efficient peptidyl transfer reaction. The CCA-adding enzyme represents an essential activity in the majority of organisms
physiological function
-
CCA-adding enzymes represent vital components of the cell's tRNA maturation and maintenance system. The CCA end, added to the tRNA by the CCA tRNA nucleotidyltransferase, is the site of aminoacylation, and aminoacyl tRNA synthetases fuse the individual amino acids to the ribose moiety of the terminal A residue. Secondly, the CCA terminus is required for the correct positioning of the aminoacyl-tRNA in the ribosome's A- and P-site in order to guarantee an efficient peptidyl transfer reaction. The CCA-adding enzyme represents an essential activity in the majority of organisms
physiological function
-
CCA-adding enzymes represent vital components of the cell's tRNA maturation and maintenance system. The CCA end, added to the tRNA by the CCA tRNA nucleotidyltransferase, is the site of aminoacylation, and aminoacyl tRNA synthetases fuse the individual amino acids to the ribose moiety of the terminal A residue. Secondly, the CCA terminus is required for the correct positioning of the aminoacyl-tRNA in the ribosome's A- and P-site in order to guarantee an efficient peptidyl transfer reaction. The CCA-adding enzyme represents an essential activity in the majority of organisms
physiological function
-
CCA-adding enzymes represent vital components of the cell's tRNA maturation and maintenance system. The CCA end, added to the tRNA by the CCA tRNA nucleotidyltransferase, is the site of aminoacylation, and aminoacyl tRNA synthetases fuse the individual amino acids to the ribose moiety of the terminal A residue. Secondly, the CCA terminus is required for the correct positioning of the aminoacyl-tRNA in the ribosome's A- and P-site in order to guarantee an efficient peptidyl transfer reaction. The CCA-adding enzyme represents an essential activity in the majority of organisms
physiological function
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tRNA-nucleotidyltransferases are RNA polymerases responsible for the synthesis of the nucleotide triplet CCA at the 3'-terminus of tRNAs. As this CCA end represents an essential functional element for aminoacylation and translation, the CCA-adding enzymes are of vital importance in all organisms. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
physiological function
-
tRNA-nucleotidyltransferases are RNA polymerases responsible for the synthesis of the nucleotide triplet CCA at the 3'-terminus of tRNAs. As this CCA end represents an essential functional element for aminoacylation and translation, the CCA-adding enzymes are of vital importance in all organisms. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
physiological function
-
tRNA-nucleotidyltransferases are RNA polymerases responsible for the synthesis of the nucleotide triplet CCA at the 3'-terminus of tRNAs. As this CCA end represents an essential functional element for aminoacylation and translation, the CCA-adding enzymes are of vital importance in all organisms. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
physiological function
-
tRNA-nucleotidyltransferases are RNA polymerases responsible for the synthesis of the nucleotide triplet CCA at the 3'-terminus of tRNAs. As this CCA end represents an essential functional element for aminoacylation and translation, the CCA-adding enzymes are of vital importance in all organisms. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
physiological function
-
tRNA-nucleotidyltransferases are RNA polymerases responsible for the synthesis of the nucleotide triplet CCA at the 3'-terminus of tRNAs. As this CCA end represents an essential functional element for aminoacylation and translation, the CCA-adding enzymes are of vital importance in all organisms. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
physiological function
-
tRNA-nucleotidyltransferases are RNA polymerases responsible for the synthesis of the nucleotide triplet CCA at the 3'-terminus of tRNAs. As this CCA end represents an essential functional element for aminoacylation and translation, the CCA-adding enzymes are of vital importance in all organisms. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
physiological function
-
tRNA-nucleotidyltransferases are RNA polymerases responsible for the synthesis of the nucleotide triplet CCA at the 3'-terminus of tRNAs. As this CCA end represents an essential functional element for aminoacylation and translation, the CCA-adding enzymes are of vital importance in all organisms. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
physiological function
-
tRNA-nucleotidyltransferases are RNA polymerases responsible for the synthesis of the nucleotide triplet CCA at the 3'-terminus of tRNAs. As this CCA end represents an essential functional element for aminoacylation and translation, the CCA-adding enzymes are of vital importance in all organisms. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
physiological function
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CCA enzymes catalyze stepwise CCA addition to the tRNA 3' end at positions 74--76 as an obligatory sequence for tRNA activity in the cell
physiological function
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CCA enzymes catalyze stepwise CCA addition to the tRNA 3' end at positions 74–76 as an obligatory sequence for tRNA activity in the cell. Only class II CCA enzymes catalyze pyrophosphorolysis, the reaction can initiate from all three CCA positions and proceed processively until the removal of nucleotide C74. Diphosphorolysis enables class II enzymes to efficiently remove an incorrect A75 nucleotide from the 3' end, at a rate much faster than the rate of A75 incorporation, suggesting the ability to perform a previously unexpected quality control mechanism for CCA synthesis
physiological function
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CCA enzymes catalyze stepwise CCA addition to the tRNA 3' end at positions 74-76 as an obligatory sequence for tRNA activity in the cell. Only class II CCA enzymes catalyze pyrophosphorolysis, the reaction can initiate from all three CCA positions and proceed processively until the removal of nucleotide C74. Diphosphorolysis enables class II enzymes to efficiently remove an incorrect A75 nucleotide from the 3' end, at a rate much faster than the rate of A75 incorporation, suggesting the ability to perform a previously unexpected quality control mechanism for CCA synthesis
physiological function
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the enzyme synthesizes and repairs the 3'-terminal CCA sequence of tRNA
physiological function
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whereas CCA is added to stable tRNAs and tRNA-like transcripts, a second CCA repeat is added to certain unstable transcripts to initiate their degradation. Following the first CCA addition cycle, nucleotide binding to the active site triggers a clockwise screw motion, producing torque on the RNA. This ejects stable RNAs, whereas unstable RNAs are refolded while bound to the enzyme and subjected to a second CCA catalytic cycle. Intriguingly, with the CCA-adding enzyme acting as a molecular vise, the RNAs proofread themselves through differential responses to its interrogation between stable and unstable substrates
physiological function
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conserved motif C in CCA-adding enzyme forms a flexible spring element modulating the relative orientation of the enzyme's head and body domains to accommodate the growing 3'-end of the tRNA. These conformational transitions initiate the rearranging of the templating amino acids to switch the specificity of the nucleotide binding pocket from CTP to ATP during CCA-synthesis
physiological function
enzyme terminates RNA synthesis after completion of 3'-CCA addition, and discriminates 3'-mature tRNA from 3'-immature tRNA. After completion of 3'-CCA addition at the catalytic site, the 3'-CCA refolds and relocates to the release site, which is discrete from the catalytic site. The 3'-CCA forms a continuously stacked, stable conformation together with the enzyme. Consequently, the 3'-mature tRNA rotates relative to the surface of the enzyme, and only the 3'-mature tRNA is ready for release. The 3'-regions of immature tRNAs cannot form the stable stacking conformation in the release site. Thus, the 3' end is relocated in the catalytic site, and the 3'-CCA is reconstructed
physiological function
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enzyme terminates RNA synthesis after completion of 3'-CCA addition, and discriminates 3'-mature tRNA from 3'-immature tRNA. After completion of 3'-CCA addition at the catalytic site, the 3'-CCA refolds and relocates to the release site, which is discrete from the catalytic site. The 3'-CCA forms a continuously stacked, stable conformation together with the enzyme. Consequently, the 3'-mature tRNA rotates relative to the surface of the enzyme, and only the 3'-mature tRNA is ready for release. The 3'-regions of immature tRNAs cannot form the stable stacking conformation in the release site. Thus, the 3' end is relocated in the catalytic site, and the 3'-CCA is reconstructed
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additional information
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structure-function relationship, overview. The enzyme binds the tRNA top half in the correct orientation for CCA-addition in a cleft, the tRNA acceptor stem interacts with a highly conserved long alpha-helical element in an almost parallel orientation. In the position of nucleotide addition, the 3'-end is bound to the active site located in the enzyme's head domain, while the T loop of the tRNA contacts the tail domain. The bound tRNA substrate remains fixed at its binding site in the enzyme during the complete nucleotide incorporation process
additional information
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structure-function relationship, overview. The active site is located in the N-terminal part of the enzyme and consists of five elements that are involved in metal ion binding, catalysis, ribose recognition, nucleotide selection, and templating. Motif A is located in the head domain and includes the general signature motif of all nucleotidyltransferases with the two metal-binding carboxylates DxD that are involved in catalysis and binding of the triphosphate moiety of the incoming nucleotides. The head domain carries motif B, where highly conserved residues play a critical role in discriminating between NTPs and dNTPs. The neck domain contains motif D, a single nucleotide-binding pocket that is specific for binding of CTP and ATP. Head and neck domain form a cleft that binds the incoming nucleotide as well as the 3'-end of the tRNA primer. The body and tail domains at the enzyme's C-terminus recognize the top-half region of the tRNA primer. The CCA-enzyme does not move along the tRNA during synthesis but remains at a fixed position
additional information
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structure-function relationship, overview. The active site is located in the N-terminal part of the enzyme and consists of five elements that are involved in metal ion binding, catalysis, ribose recognition, nucleotide selection, and templating. Motif A is located in the head domain and includes the general signature motif of all nucleotidyltransferases with the two metal-binding carboxylates DxD that are involved in catalysis and binding of the triphosphate moiety of the incoming nucleotides. The head domain carries motif B, where highly conserved residues play a critical role in discriminating between NTPs and dNTPs. The neck domain contains motif D, a single nucleotide-binding pocket that is specific for binding of CTP and ATP. Head and neck domain form a cleft that binds the incoming nucleotide as well as the 3'-end of the tRNA primer. The body and tail domains at the enzyme's C-terminus recognize the top-half region of the tRNA primer. The CCA-enzyme does not move along the tRNA during synthesis but remains at a fixed position
additional information
-
structure-function relationship, overview. The active site is located in the N-terminal part of the enzyme and consists of five elements that are involved in metal ion binding, catalysis, ribose recognition, nucleotide selection, and templating. Motif A is located in the head domain and includes the general signature motif of all nucleotidyltransferases with the two metal-binding carboxylates DxD that are involved in catalysis and binding of the triphosphate moiety of the incoming nucleotides. The head domain carries motif B, where highly conserved residues play a critical role in discriminating between NTPs and dNTPs. The neck domain contains motif D, a single nucleotide-binding pocket that is specific for binding of CTP and ATP. Head and neck domain form a cleft that binds the incoming nucleotide as well as the 3'-end of the tRNA primer. The body and tail domains at the enzyme's C-terminus recognize the top-half region of the tRNA primer. The CCA-enzyme does not move along the tRNA during synthesis but remains at a fixed position
additional information
-
structure-function relationship, overview. The active site is located in the N-terminal part of the enzyme and consists of five elements that are involved in metal ion binding, catalysis, ribose recognition, nucleotide selection, and templating. Motif A is located in the head domain and includes the general signature motif of all nucleotidyltransferases with the two metal-binding carboxylates DxD that are involved in catalysis and binding of the triphosphate moiety of the incoming nucleotides. The head domain carries motif B, where highly conserved residues play a critical role in discriminating between NTPs and dNTPs. The neck domain contains motif D, a single nucleotide-binding pocket that is specific for binding of CTP and ATP. Head and neck domain form a cleft that binds the incoming nucleotide as well as the 3'-end of the tRNA primer. The body and tail domains at the enzyme's C-terminus recognize the top-half region of the tRNA primer. The CCA-enzyme does not move along the tRNA during synthesis but remains at a fixed position
additional information
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in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
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class 1 enzymes have a tRNA-binding body domain consisting of a beta sheet with flanking alpha helices. Head and neck domains form the active site and are also composed of alpha-helical and beta-sheet elements, structure-function relationship, overview
additional information
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in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
-
in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
-
in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
-
in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
-
in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
-
in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
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the CCA enzymes are unusual RNA polymerases, which catalyze CCA addition to positions 74-76 at the tRNA 3' end without using a nucleic acid template, reaction mechanism of CCA addition, overview
additional information
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the CCA enzymes are unusual RNA polymerases, which catalyze CCA addition to positions 74-76 at the tRNA 3' end without using a nucleic acid template, reaction mechanism of CCA addition and reverse phosphorolysis reaction, overview
additional information
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the CCA enzymes are unusual RNA polymerases, which catalyze CCA addition to positions 74-76 at the tRNA 3' end without using a nucleic acid template, reaction mechanism of CCA addition and reverse phosphorolysis reaction, overview
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SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
a tRNA(Ala) precursor + 2 CTP + ATP
a tRNA(Ala) with a 3' CCA end + 3 diphosphate
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synthesizes poly(C) when incubated with CTP alone, but switches to synthesize CCA when incubated with both CTP and ATP. The enzyme also exhibits a processing activity that removes nucleotides in the 3' to 5' direction to as far as position 74
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-
?
tRNA(Phe) precursor + 2 CTP + ATP
tRNA(Phe) with a 3' CCA end + 3 diphosphate
-
the 48 kDa monomer forms a stable salt-resistant dimer in solution. Further dimerization of the dimeric enzyme to form a tetramer is induced by the binding of two tRNA molecules. The formation of a tetramer with only two bound tRNA molecules leads to the suggestion that one pair of active sites may be specific for adding two C bases, which results in scrunching of the primer strand. An adjacent second pair of active sites may be specific for adding A after addition of two C bases which makes the 30 terminus long enough to reach the second pair of active sites
-
-
?
tRNACys + 2 CTP + ATP
tRNACys with 3'-CCA end + 3 diphosphate
-
insertional editing of substrate is not required for addition of the CCA sequence by CCase
-
-
?
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
-
-
-
?
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
substrate is synthetic DNA templates based on the sequence of Escherichia coli tRNAVal. Overall reaction
-
-
r
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
the 30-region of RNA is proofread, after two nucleotide additions, in the closed, active form of the complex at the AMP incorporation stage. This proofreading is a prerequisite for the maintenance of fidelity for complete CCA synthesis
-
-
?
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
tRNA does not rotate or translocate during C74 addition. A single flexible beta-turn orchestrates consecutive addition of all three nucleotides without significant movement of the tRNA on the enzyme surface
-
-
?
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
-
-
-
r
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
substrate is synthetic DNA templates based on the sequence of Escherichia coli tRNAVal. Overall reaction, class II CCA-adding enzymes also perform the reverse reaction, mechanism, overview. The enzyme catalyzes diphosphorolysis slowly relative to the forward nucleotide addition and that it exhibits weak binding affinity to diphosphate relative to NTP
-
-
r
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
-
-
-
r
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
-
-
-
?
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
substrate is synthetic DNA templates based on the sequence of Escherichia coli tRNAVal. Overall reaction, class II CCA-adding enzymes also perform the reverse reaction, mechanism, overview. The enzyme catalyzes diphosphorolysis slowly relative to the forward nucleotide addition and that it exhibits weak binding affinity to diphosphate relative to NTP
-
-
r
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
overall reaction
-
-
?
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
one catalytic center is responsible for addition of both CTP and ATP. As the single active site catalyzes addition of each nucleotide, the growing 3'-end of the tRNA would progressively refold to create a binding pocket for addition of the next nucleotide
-
-
?
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3'CCA end + 3 diphosphate
-
-
-
-
?
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3'CCA end + 3 diphosphate
-
-
-
-
?
a tRNA precursor + CTP
a tRNA with a 3' cytidine end + diphosphate
-
C74 addition
-
-
?
a tRNA precursor + CTP
a tRNA with a 3' cytidine end + diphosphate
-
-
-
?
a tRNA precursor + CTP
a tRNA with a 3' cytidine end + diphosphate
-
one catalytic center is responsible for addition of both CTP and ATP. As the single active site catalyzes addition of each nucleotide, the growing 3'-end of the tRNA would progressively refold to create a binding pocket for addition of the next nucleotide
-
-
?
a tRNA with a 3' CC end + ATP
a tRNA with a 3' CCA end + diphosphate
-
-
-
-
?
a tRNA with a 3' CC end + ATP
a tRNA with a 3' CCA end + diphosphate
-
A76 addition
-
-
?
a tRNA with a 3' CC end + ATP
a tRNA with a 3' CCA end + diphosphate
-
-
-
?
a tRNA with a 3' CC end + ATP
a tRNA with a 3' CCA end + diphosphate
-
one catalytic center is responsible for addition of both CTP and ATP. As the single active site catalyzes addition of each nucleotide, the growing 3'-end of the tRNA would progressively refold to create a binding pocket for addition of the next nucleotide
-
-
?
a tRNA with a 3' CCA end + 3 diphosphate
a tRNA precursor + 2 CTP + ATP
-
-
-
-
r
a tRNA with a 3' CCA end + 3 diphosphate
a tRNA precursor + 2 CTP + ATP
-
substrate is synthetic DNA templates based on the sequence of Escherichia coli tRNAVal. Overall reaction, class II CCA-adding enzymes also perform the reverse reaction, mechanism, overview. The enzyme catalyzes diphosphorolysis slowly relative to the forward nucleotide addition and that it exhibits weak binding affinity to diphosphate relative to NTP
-
-
r
a tRNA with a 3' CCA end + 3 diphosphate
a tRNA precursor + 2 CTP + ATP
-
-
-
-
r
a tRNA with a 3' CCA end + 3 diphosphate
a tRNA precursor + 2 CTP + ATP
-
substrate is synthetic DNA templates based on the sequence of Escherichia coli tRNAVal. Overall reaction, class II CCA-adding enzymes also perform the reverse reaction, mechanism, overview. The enzyme catalyzes diphosphorolysis slowly relative to the forward nucleotide addition and that it exhibits weak binding affinity to diphosphate relative to NTP
-
-
r
a tRNA with a 3' cytidine + CTP
a tRNA with a 3' CC end + diphosphate
-
-
-
-
?
a tRNA with a 3' cytidine + CTP
a tRNA with a 3' CC end + diphosphate
-
C75 addition
-
-
?
a tRNA with a 3' cytidine + CTP
a tRNA with a 3' CC end + diphosphate
-
-
-
?
a tRNA with a 3' cytidine + CTP
a tRNA with a 3' CC end + diphosphate
-
one catalytic center is responsible for addition of both CTP and ATP. As the single active site catalyzes addition of each nucleotide, the growing 3'-end of the tRNA would progressively refold to create a binding pocket for addition of the next nucleotide
-
-
?
deoxynucleoside triphosphate + DNAn
diphosphate + DNAn+1
-
the specific recognition of deaminated bases by polymerase PolB1 may represent an initial step in their repair while polymerase PolY1 may be involved in damage tolerance at the replication fork. The deaminated bases can be introduced into DNA enzymatically, since both PolB1 and PolY1 are able to incorporate the aberrant DNA precursors dUTP and dITP
-
-
?
deoxynucleoside triphosphate + DNAn
diphosphate + DNAn+1
-
specifically recognizes the presence of the deaminated bases hypoxanthine and uracil in the template by stalling DNA polymerization 3-4 bases upstream of these lesions and strongly associates with oligonucleotides containing them. PolB1 also stops at 8-oxoguanine and is unable to bypass an abasic site in the template. The deaminated bases can be introduced into DNA enzymatically, since both PolB1 and PolY1 are able to incorporate the aberrant DNA precursors dUTP and dITP
-
-
?
deoxynucleoside triphosphate + DNAn
diphosphate + DNAn+1
-
the specific recognition of deaminated bases by polymerase PolB1 may represent an initial step in their repair while polymerase PolY1 may be involved in damage tolerance at the replication fork. The deaminated bases can be introduced into DNA enzymatically, since both PolB1 and PolY1 are able to incorporate the aberrant DNA precursors dUTP and dITP
-
-
?
deoxynucleoside triphosphate + DNAn
diphosphate + DNAn+1
-
specifically recognizes the presence of the deaminated bases hypoxanthine and uracil in the template by stalling DNA polymerization 3-4 bases upstream of these lesions and strongly associates with oligonucleotides containing them. PolB1 also stops at 8-oxoguanine and is unable to bypass an abasic site in the template. The deaminated bases can be introduced into DNA enzymatically, since both PolB1 and PolY1 are able to incorporate the aberrant DNA precursors dUTP and dITP
-
-
?
tRNAAsp with a 3' CC end + ATP
tRNAAsp with a 3' CCA end + diphosphate
-
usage of tRNAAsp of Bacillus subtilis as substrate, and 5'-labeled tRNA-C and 3'-labeled tRNA-CC alkylated by ethylnitrosourea
-
-
?
tRNAAsp with a 3' CC end + ATP
tRNAAsp with a 3' CCA end + diphosphate
-
usage of tRNAAsp of Bacillus subtilis as substrate, and 5'-labeled tRNA-C and 3'-labeled tRNA-CC alkylated by ethylnitrosourea
-
-
?
tRNAAsp with a 3' cytidine + CTP
tRNAAsp with a 3' CC end + diphosphate
-
usage of tRNAAsp of Bacillus subtilis as substrate, and 5'-labeled tRNA-C and 3'-labeled tRNA-CC alkylated by ethylnitrosourea
-
-
?
tRNAAsp with a 3' cytidine + CTP
tRNAAsp with a 3' CC end + diphosphate
-
usage of tRNAAsp of Bacillus subtilis as substrate, and 5'-labeled tRNA-C and 3'-labeled tRNA-CC alkylated by ethylnitrosourea
-
-
?
tRNAX1 + ATP + 2 CTP
tRNAXCCA + 3 diphosphate
-
only one protein is responsible for both AMP and CMP incorporation
-
-
r
tRNAX1 + ATP + 2 CTP
tRNAXCCA + 3 diphosphate
Escherichia coli B / ATCC 11303
-
only one protein is responsible for both AMP and CMP incorporation
-
-
r
yeast tRNAPhe + 2 CTP + ATP
yeast tRNAPhe with 3'-CCA end + 3 diphosphate
-
preparation of substrate lacking the CCA-terminus or ending with a partial CCA-end
-
-
?
yeast tRNAPhe + 2 CTP + ATP
yeast tRNAPhe with 3'-CCA end + 3 diphosphate
-
preparation of substrate lacking the CCA-terminus or ending with a partial CCA-end
-
-
?
yeast tRNAPhe + 2 CTP + ATP
yeast tRNAPhe with 3'-CCA end + 3 diphosphate
-
preparation of substrate lacking the CCA-terminus or ending with a partial CCA-end
-
-
?
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
class 2 enzymes select the nucleotides to be incorporated by a true amino acid template that consists of the three highly conserved residues glutamic acid, aspartic acid and arginine (EDxxR). The arginine residue forms hydrogen bonds with ATP (1 bond) and CTP (2 bonds), assisted by aspartate that contributes one hydrogen bond
-
-
-
additional information
?
-
in Aquifex aeolicus, 3'-terminal CCA (CCA-3' at positions 74-76) of tRNA is synthesized by CC-adding and A-adding enzymes collaboratively. CC addition onto tRNA is catalyzed by poly A polymerase. After C74 addition in an enclosed active pocket and diphosphate release, the tRNA translocates and rotates relative to the enzyme, and C75 addition occurs in the same active pocket as C74 addition. At both the C74-adding and C75-adding stages, CTP is selected by Watson-Crick-like hydrogen bonds between the cytosine of CTP and conserved Asp and Arg residues in the pocket. After C74C75 addition and diphosphate release, the tRNA translocates further and drops off the enzyme
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
class 1 enzymes recognize and select the correct nucleotides not as pure protein-based enzymes, but as ribonucleoproteins, where the tRNA part is not just a substrate molecule (primer), but is an active part of the nucleotide binding pocket
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
class I CCA enzymes do not catalyze diphosphorolysis in contrast to class II CCA enzymes, overview
-
-
-
additional information
?
-
-
tRNA minihelices, which contain only the acceptor stem and TPsiC stem-loop, are also efficiently subjected to CCACCA addition when they have guanosines at the first and second positions as well as a destabilized acceptor stem by virtue of mismatches and G-U wobbles
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
class 2 enzymes select the nucleotides to be incorporated by a true amino acid template that consists of the three highly conserved residues glutamic acid, aspartic acid and arginine (EDxxR). The arginine residue forms hydrogen bonds with ATP (1 bond) and CTP (2 bonds), assisted by aspartate that contributes one hydrogen bond
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
class 2 enzymes select the nucleotides to be incorporated by a true amino acid template that consists of the three highly conserved residues glutamic acid, aspartic acid and arginine (EDxxR). The arginine residue forms hydrogen bonds with ATP (1 bond) and CTP (2 bonds), assisted by aspartate that contributes one hydrogen bond
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
class 2 enzymes select the nucleotides to be incorporated by a true amino acid template that consists of the three highly conserved residues glutamic acid, aspartic acid and arginine (EDxxR). The arginine residue forms hydrogen bonds with ATP (1 bond) and CTP (2 bonds), assisted by aspartate that contributes one hydrogen bond
-
-
-
additional information
?
-
-
the CCA-adding enzymes can use three different substrates: tRNAs lacking one, i.e. tRNA-CC, two, i.e. tRNA-C, or all three 3'-terminal nucleotides, tRNA. The CCA-adding enzyme recognizes primarily the top half tRNA minihelix
-
-
-
additional information
?
-
the HD domain of the enzyme also exhibits 2',3'-cyclic phosphodiesterase, 2'-nucleotidase, and Ni2+-dependent phosphatase activities, overview
-
-
-
additional information
?
-
-
the tRNA substrate must remain fixed on the enzyme surface during CA addition. Both CTP addition to tRNA-C and ATP addition to tRNA-CC are dramatically inhibited by alkylation of the same tRNA phosphates in the acceptor stem and TPsiC stem-loop
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
class 2 enzymes select the nucleotides to be incorporated by a true amino acid template that consists of the three highly conserved residues glutamic acid, aspartic acid and arginine (EDxxR). The arginine residue forms hydrogen bonds with ATP (1 bond) and CTP (2 bonds), assisted by aspartate that contributes one hydrogen bond
-
-
-
additional information
?
-
-
only class II CCA enzymes catalyze diphosphorolysis, the reaction can initiate from all three CCA positions and proceed processively until the removal of nucleotide C74. Diphosphorolysis enables class II enzymes to efficiently remove an incorrect A75 nucleotide from the 3' end, at a rate much faster than the rate of A75 incorporation, suggesting the ability to perform a previously unexpected quality control mechanism for CCA synthesis. No activity with non-tRNA substrate U2 snRNA, but EcCCA is active with non-tRNA substrate BMV TLSTyr and removes the terminalA nucleotide without proceeding further. The enzyme shows a robust activity with tRNA-A75, degrading it down to tRNA-A73 (by 50%) while showing a minor activity with tRNA-C76 (less than 5% substrate conversion) and no activity with tRNA-A74. The incorrect A75 is more readily removed than it is synthesized, suggesting a quality control mechanism that can improve the overall accuracy of CCA synthesis
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
NTSFIII is inactive with CTP and tRNAAsp-C as substrates
-
-
-
additional information
?
-
-
the enzyme catalyses a unique template-independent but sequence-specific nucleotide polymerization reaction, active site structure and molecular mechanism, overview. Construction of a corkscrew model for CCA addition that includes a fixed active site and a traveling tRNA-binding region formed by flexible parts of the protein
-
-
-
additional information
?
-
the enzyme catalyses a unique template-independent but sequence-specific nucleotide polymerization reaction, active site structure and molecular mechanism, overview. Construction of a corkscrew model for CCA addition that includes a fixed active site and a traveling tRNA-binding region formed by flexible parts of the protein
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
class 2 enzymes select the nucleotides to be incorporated by a true amino acid template that consists of the three highly conserved residues glutamic acid, aspartic acid and arginine (EDxxR). The arginine residue forms hydrogen bonds with ATP (1 bond) and CTP (2 bonds), assisted by aspartate that contributes one hydrogen bond
-
-
-
additional information
?
-
-
only class II CCA enzymes catalyze diphosphorolysis, the reaction can initiate from all three CCA positions and proceed processively until the removal of nucleotide C74. Diphosphorolysis enables class II enzymes to efficiently remove an incorrect A75 nucleotide from the 3' end, at a rate much faster than the rate of A75 incorporation, suggesting the ability to perform a previously unexpected quality control mechanism for CCA synthesis. No activity with non-tRNA substrate BMVTLSTyr or U2 snRNA. The enzyme shows a robust activity with tRNA-A75, degrading it down to tRNA-A73 (by 50%) while showing a minor activity with tRNA-C76 (less than 5% substrate conversion) and no activity with tRNA-A74. The incorrect A75 is more readily removed than it is synthesized, suggesting a quality control mechanism that can improve the overall accuracy of CCA synthesis
-
-
-
additional information
?
-
-
the CCA-adding enzymes can use three different substrates: tRNAs lacking one, i.e. tRNA-CC, two, i.e. tRNA-C, or all three 3'-terminal nucleotides, tRNA. The Sulfolobus shibatae CCA-adding enzyme forms a stable complex with tRNA. The CCA-adding enzyme recognizes primarily the top half tRNA minihelix
-
-
-
additional information
?
-
-
the tRNA substrate must remain fixed on the enzyme surface during CA addition, tRNA-C cross-linked to the enzyme remains fully active for addition of CTP and ATP. The growing 3'-terminus of the tRNA progressively refolds to allow the solitary active site to reuse a single CTP binding site. The ATP binding site is then created collaboratively by the refolded CCterminus and the enzyme, and nucleotide addition ceases when the nucleotide binding pocket is full. The template for CCA addition is a dynamic ribonucleoprotein structure. Both CTP addition to tRNA-C and ATP addition to tRNA-CC are dramatically inhibited by alkylation of the same tRNA phosphates in the acceptor stem and TPsiC stem-loop
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
class 2 enzymes select the nucleotides to be incorporated by a true amino acid template that consists of the three highly conserved residues glutamic acid, aspartic acid and arginine (EDxxR). The arginine residue forms hydrogen bonds with ATP (1 bond) and CTP (2 bonds), assisted by aspartate that contributes one hydrogen bond
-
-
-
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
-
-
-
?
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
-
-
-
r
a tRNA precursor + 2 CTP + ATP
a tRNA with a 3' CCA end + 3 diphosphate
-
-
-
-
r
a tRNA with a 3' CCA end + 3 diphosphate
a tRNA precursor + 2 CTP + ATP
-
-
-
-
r
a tRNA with a 3' CCA end + 3 diphosphate
a tRNA precursor + 2 CTP + ATP
-
-
-
-
r
deoxynucleoside triphosphate + DNAn
diphosphate + DNAn+1
-
the specific recognition of deaminated bases by polymerase PolB1 may represent an initial step in their repair while polymerase PolY1 may be involved in damage tolerance at the replication fork. The deaminated bases can be introduced into DNA enzymatically, since both PolB1 and PolY1 are able to incorporate the aberrant DNA precursors dUTP and dITP
-
-
?
deoxynucleoside triphosphate + DNAn
diphosphate + DNAn+1
-
the specific recognition of deaminated bases by polymerase PolB1 may represent an initial step in their repair while polymerase PolY1 may be involved in damage tolerance at the replication fork. The deaminated bases can be introduced into DNA enzymatically, since both PolB1 and PolY1 are able to incorporate the aberrant DNA precursors dUTP and dITP
-
-
?
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
the CCA-adding enzymes can use three different substrates: tRNAs lacking one, i.e. tRNA-CC, two, i.e. tRNA-C, or all three 3'-terminal nucleotides, tRNA. The CCA-adding enzyme recognizes primarily the top half tRNA minihelix
-
-
-
additional information
?
-
P06961
the HD domain of the enzyme also exhibits 2',3'-cyclic phosphodiesterase, 2'-nucleotidase, and Ni2+-dependent phosphatase activities, overview
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
the enzyme catalyses a unique template-independent but sequence-specific nucleotide polymerization reaction, active site structure and molecular mechanism, overview. Construction of a corkscrew model for CCA addition that includes a fixed active site and a traveling tRNA-binding region formed by flexible parts of the protein
-
-
-
additional information
?
-
Q96Q11
the enzyme catalyses a unique template-independent but sequence-specific nucleotide polymerization reaction, active site structure and molecular mechanism, overview. Construction of a corkscrew model for CCA addition that includes a fixed active site and a traveling tRNA-binding region formed by flexible parts of the protein
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
additional information
?
-
-
the CCA-adding enzymes can use three different substrates: tRNAs lacking one, i.e. tRNA-CC, two, i.e. tRNA-C, or all three 3'-terminal nucleotides, tRNA. The Sulfolobus shibatae CCA-adding enzyme forms a stable complex with tRNA. The CCA-adding enzyme recognizes primarily the top half tRNA minihelix
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
CCA-adding enzymes recognize tRNA and tRNA-like structures as substrates, select and discriminate the correct nucleotides CTP and ATP against UTP and GTP, and, after incorporation of two C residues, the nucleotide specificity has to switch towards ATP without the help of a nucleic acid template. The enzymes have to stop polymerization exactly after three positions and recognize partial CCA-ends and add only the missing residues for completion, instead of stubbornly adding CCA-ends to their substrates, overview
-
-
-
additional information
?
-
-
the specific enzyme incorporates only a highly restricted number of nucleotides in a tRNA primer and then stops polymerization at a high efficiency and accuracy. It selects exclusively CTP and ATP for incorporation and discriminates strongly against the other two nucleotide triphosphates. It does not require a nucleic acid template for directing order and nature of nucleotides to be inserted and is highly selective for tRNA-like structures as a polymerization substrate. The enzyme fulfills both functions in maintenance/repair as well as de novo polymerization
-
-
-
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Mg2+
Mn2+
-
while Mn2+ is incompetent for diphosphorolysis of tRNA-A76, it promotes a more rapid forward synthesis of tRNA-A76 than even the Mg2+ ion
Zn2+
-
it is inert for diphosphorolysis of tRNAA76, but it is active in the forward synthesis of this tRNA
additional information
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction
Mg2+
-
two metal ions are bound to the two catalytically important carboxylates. The first metal ion deprotonates the 3'-OH group of the tRNA primer and activates the resulting 3'-O for an attack at the a-phosphate of the incoming nucleotide. The second metal ion stabilizes the triphosphate moiety of the NTP and facilitates the leaving of the pyrophosphate group, overview
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction. The Mg2+ ions are also required for the diposphorolysis reaction, overview. With tRNA-A76 as the substrate in the reverse reacction, only Mg2+ is catalytically competent
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction. The Mg2+ ions are also required for the diposphorolysis reaction, overview
Mg2+
-
essentially required, two metal ions are coordinated by highly conserved carboxylates and fulfill specific roles in catalyzing the reaction. Metal ion A activates the 3'-hydroxyl group of the primer for a nucleophilic in-line attack on the alpha-phosphate of the incoming NTP, while metal ion B promotes the leaving of the diphosphate group that is released during this reaction
additional information
-
the nature of the divalent metal ions can influence the positioning of diphosphate in the active site
additional information
-
Mn2+ cannot substitute for Mg2+
additional information
-
the nature of the divalent metal ions can influence the positioning of diphosphate in the active site. tRNAs ending in C75 and C74, in contrast to tRNA A76, are also active with other divalent metal ions tan Mg2+, albeit less efficient due to accumulation of unreacted tRNA substrate. Diphosphorolysis of tRNA-C75 proceeds the farthest with Mg2+, followed by Co2+, and by Mn2+ and Ni2+. Pyrophosphorolysis of tRNA-C74 also proceeds the farthest with Mg2+, but it is followed by Mn2+ and Co2+ and followed by Ni2+. While the preference of divalent metal ions varies among the three reactions, it also differs from that required for the forward A76 addition. While Ca2+ and Pb2+ fail to promote diphosphorolysis of all three tRNA substrates, they also fail to promote forward synthesis of tRNA-A76 for EcCCA
additional information
-
the nature of the divalent metal ions can influence the positioning of diphosphate in the active site
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INHIBITORS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
1,10-phenanthroline
-
inhibition of AMP incorporating activity only, the CMP incorporating activity is much less sensitive
2,2,2-Terpyridyl
-
inhibition of AMP incorporating activity only, the CMP incorporating activity is much less sensitive
2,2-dipyridyl
-
at high concentrations, inhibition of AMP incorporating activity only, the CMP incorporating activity is much less sensitive
bathophenanthroline
-
inhibition of AMP incorporating activity only, the CMP incorporating activity is much less sensitive
ethylnitrosourea
-
both CTP addition to tRNA-C and ATP addition to tRNA-CC are dramatically inhibited by alkylation of the same tRNA phosphates in the acceptor stem and TPsiC stem-loop
ethylnitrosourea
-
both CTP addition to tRNA-C and ATP addition to tRNA-CC are dramatically inhibited by alkylation of the same tRNA phosphates in the acceptor stem and TPsiC stem-loop
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
ACTIVATING COMPOUND
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
protein Hfq
-
the multifunctional protein Hfq, originally discovered as a host factor for phage Qb, can stimulate the CCA-adding activity, Hfq facilitates the release of the reaction product, after CCA addition has taken place
-
protein Hfq
-
the multifunctional protein Hfq, originally discovered as a host factor for phage Qb, can stimulate the CCA-adding activity, Hfq facilitates the release of the reaction product, after CCA addition has taken place
-
protein Hfq
-
the multifunctional protein Hfq, originally discovered as a host factor for phage Qb, can stimulate the CCA-adding activity, Hfq facilitates the release of the reaction product, after CCA addition has taken place
-
protein Hfq
-
the multifunctional protein Hfq, originally discovered as a host factor for phage Qb, can stimulate the CCA-adding activity, Hfq facilitates the release of the reaction product, after CCA addition has taken place
-
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
KM VALUE [mM]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.008
a tRNA precursor
-
mutant D139A, pH not specified in the publication, temperature not specified in the publication
-
0.012
a tRNA precursor
-
the mutant with alterations at the extreme C-terminus of the tail domain, pH 9.0, 37°C; wild-type, pH 9.0, 37°C
-
0.119
a tRNA precursor
-
wild-type, pH not specified in the publication, temperature not specified in the publication
-
0.233
ATP
-
A76 addition, pH and temperature not specified in the publication, mutant enzyme P295G
0.3
ATP
-
A76 addition, pH and temperature not specified in the publication, wild-type enzyme
0.35
ATP
-
A76 addition, pH and temperature not specified in the publication, mutant enzyme P295T
7.64
ATP
-
A76 addition, pH and temperature not specified in the publication, mutant enzyme P295A
12.5
ATP
-
A76 addition, pH and temperature not specified in the publication, mutant enzyme P295SA
0.01
CTP
-
C74 addition, pH and temperature not specified in the publication, mutant enzyme P295G; C74 addition, pH and temperature not specified in the publication, wild-type enzyme
0.025
CTP
-
C74 addition, pH and temperature not specified in the publication, mutant enzyme P295T; C75 addition, pH and temperature not specified in the publication, mutant enzyme P295T
0.037
CTP
-
C74 addition, pH and temperature not specified in the publication, mutant enzyme P295A
0.04
CTP
-
C75 addition, pH and temperature not specified in the publication, mutant enzyme P295A
0.09
CTP
-
C75 addition, pH and temperature not specified in the publication, mutant enzyme P295G
0.175
CTP
-
C75 addition, pH and temperature not specified in the publication, wild-type enzyme
0.2
CTP
-
C74 addition, pH and temperature not specified in the publication, mutant enzyme P295SA
0.65
CTP
-
C75 addition, pH and temperature not specified in the publication, mutant enzyme P295SA
0.5
diphosphate
-
pH not specified in the publication, 37°C, diphosphorolysis reaction with substrate tRNA-C75
0.6
diphosphate
-
pH not specified in the publication, 37°C, diphosphorolysis reaction with substrate tRNA-C74
1
diphosphate
-
pH not specified in the publication, 37°C, diphosphorolysis reaction with substrate tRNA-A76
additional information
ATP
-
pH 9.0, 70°C, the initial velocity is a linear function of ATP from 0.015 to 0.2 mM, suugesting that the Km for ATP in presence of each UTP, GTP and CTP is much higher than 0.03 mM
additional information
additional information
-
kinetic parameters of diphosphorolysis from A76, C75, and C74, overview
-
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TURNOVER NUMBER [1/s]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.09
a tRNA precursor
-
wild-type, pH not specified in the publication, temperature not specified in the publication
-
0.11
a tRNA precursor
-
mutant D139A, pH not specified in the publication, temperature not specified in the publication
-
0.76
ATP
-
A76 addition, pH and temperature not specified in the publication, mutant enzyme P295SA
0.83
ATP
-
A76 addition, pH and temperature not specified in the publication, mutant enzyme P295A
2.55
ATP
-
A76 addition, pH and temperature not specified in the publication, mutant enzyme P295G
2.56
ATP
-
A76 addition, pH and temperature not specified in the publication, wild-type enzyme
2.72
ATP
-
A76 addition, pH and temperature not specified in the publication, mutant enzyme P295T
1.83
CTP
-
C75 addition, pH and temperature not specified in the publication, mutant enzyme P295SA
2.46
CTP
-
C75 addition, pH and temperature not specified in the publication, mutant enzyme P295G
2.48
CTP
-
C75 addition, pH and temperature not specified in the publication, mutant enzyme P295A
2.55
CTP
-
C74 addition, pH and temperature not specified in the publication, mutant enzyme P295SA
2.93
CTP
-
C75 addition, pH and temperature not specified in the publication, mutant enzyme P295T
3.21
CTP
-
C75 addition, pH and temperature not specified in the publication, wild-type enzyme
3.43
CTP
-
C74 addition, pH and temperature not specified in the publication, mutant enzyme P295G
3.53
CTP
-
C74 addition, pH and temperature not specified in the publication, mutant enzyme P295A
3.68
CTP
-
C74 addition, pH and temperature not specified in the publication, wild-type enzyme
3.8
CTP
-
C74 addition, pH and temperature not specified in the publication, mutant enzyme P295T
1.4
diphosphate
-
pH not specified in the publication, 37°C, diphosphorolysis reaction with substrate tRNA-A76
1.9
diphosphate
-
pH not specified in the publication, 37°C, diphosphorolysis reaction with substrate tRNA-C75
3.1
diphosphate
-
pH not specified in the publication, 37°C, diphosphorolysis reaction with substrate tRNA-C74
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
kcat/KM VALUE [1/mMs-1]
SUBSTRATE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
0.07
a tRNA precursor
-
mutant D139A, pH not specified in the publication, temperature not specified in the publication
-
1.23
a tRNA precursor
-
wild-type, pH not specified in the publication, temperature not specified in the publication
-
1.4
diphosphate
-
pH not specified in the publication, 37°C, diphosphorolysis reaction with substrate tRNA-A76
3.8
diphosphate
-
pH not specified in the publication, 37°C, diphosphorolysis reaction with substrate tRNA-C75
5.2
diphosphate
-
pH not specified in the publication, 37°C, diphosphorolysis reaction with substrate tRNA-C74
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
SPECIFIC ACTIVITY [µmol/min/mg]
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
67.1
-
purified enzyme, pH not specified in the publication, 37°C, pooled column fraction
280
-
purified enzyme, pH not specified in the publication, 37°C, column peak fraction
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pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Please wait a moment until the data is sorted. This message will disappear when the data is sorted.
pH RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
7 - 10
-
the enzyme exhibits substantial activity over a broad range from pH 7 to 10
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TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
25
37
70
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TEMPERATURE RANGE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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pI VALUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
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SOURCE TISSUE
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SOURCE
-
TRNT1 protein levels are 10fold lower in muscle than in fibroblasts
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LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
-
the first five amino acids of the N-terminal signal sequence are required for efficient translocation into mitochondria. Variants lacking the first start codon show less mitochondrial import. Mutations in the mature domain reduce the localization tomitochondria and in turn enhance the translocation into chloroplasts
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PDB
SCOP
CATH
ORGANISM
UNIPROT
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Archaeoglobus fulgidus (strain ATCC 49558 / VC-16 / DSM 4304 / JCM 9628 / NBRC 100126)
Thermotoga maritima (strain ATCC 43589 / MSB8 / DSM 3109 / JCM 10099)
Thermotoga maritima (strain ATCC 43589 / MSB8 / DSM 3109 / JCM 10099)
Thermotoga maritima (strain ATCC 43589 / MSB8 / DSM 3109 / JCM 10099)
Thermotoga maritima (strain ATCC 43589 / MSB8 / DSM 3109 / JCM 10099)
Thermotoga maritima (strain ATCC 43589 / MSB8 / DSM 3109 / JCM 10099)
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MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
48000
48000
-
2 * 48000, the 48 kDa monomer forms a stable salt-resistant dimer in solution. Further dimerization of the dimeric enzyme to form a tetramer is induced by the binding of two tRNA molecules
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SUBUNITS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
dimer
-
2 * 48000, the 48 kDa monomer forms a stable salt-resistant dimer in solution. Further dimerization of the dimeric enzyme to form a tetramer is induced by the binding of two tRNA molecules
monomer
tetramer
-
2 * 48000, the 48 kDa monomer forms a stable salt-resistant dimer in solution. Further dimerization of the dimeric enzyme to form a tetramer is induced by the binding of two tRNA molecules
additional information
additional information
-
in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
-
class 1 enzymes have a tRNA-binding body domain consisting of a beta sheet with flanking alpha helices. Head and neck domains form the active site and are also composed of alpha-helical and beta-sheet elements, structure-function relationship, overview
additional information
-
in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
-
in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
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in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
the enzyme comprises two domains: an N-terminal domain containing the nucleotidyltransferase activity and a C-terminal HD domain
additional information
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in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
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four domain architecture with a cluster of conserved residues forming a positively charged cleft between the first two domains, modeling of human mitochondrial tRNA-nucleotidyltransferase monomer
additional information
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class II enzymes found in bacteria and eukaryotes carry a flexible loop in their catalytic core required for switching the specificity of the nucleotide binding pocket from CTP- to ATP-recognition, with the existence of conserved loop families. Loop replacements within families do not interfere with enzymatic activity. Modeling experiments suggest specific interactions of loop positions with important elements of the protein, forming a lever-like structure
additional information
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in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
additional information
-
in class 2 enzymes, only the head domain carries a beta-sheet and forms the nucleotidyltransferase core, while neck, body and tail consist exclusively of alpha helices, giving the enzyme a hook- or seahorse-like overall structure, structure-function relationship, overview
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Crystallization/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
cocrystal structures of the enzyme complexed with both a tRNA mimic and nucleoside triphosphates under catalytically active conditions. The structures suggest that adenosine 5'-monophosphate is incorporated onto the A76 position of the tRNA via a carboxylate-assisted, one-metal-ion mechanism with aspartate 110 functioning as a general base. The discrimination against incorporation of cytidine 5'-triphosphate at position 76 arises from improper placement of the a phosphate of the incoming CTP, which results from the interaction of C with arginine 224 and prevents the nucleophilic attack by the 3' hydroxyl group of cytidine75
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cocrystallisation of enzyme complexes with nine distinct tRNA minihelices. All of the binary and ternary complex crystals belong to the space group P4(3)2(1)2, and contain one complex molecule in the asymmetric unit. Crystal structures are solved at 2.5 to 3.05 A resolutions by molecular replacement
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crystal structures of the CCA-adding enzyme, and its complexes with CTP and ATP at 2.0, 2.0 and 2.7 A resolutions, respectively
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hanging-drop vapour diffusion method at 4°C, crystal structure of the enzyme in complex with tRNA
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in complex with a human MenBeta minihelix. The unstable minihelix is bound between the enzyme’s catalytic center, comprised of the head and neck domains, and its tail domain. The minihelix perfectly mimics full-length tRNA with its acceptor and TPsiC stems folding into a continuous A-type RNA helix. The TPsiC loop is in the same conformation as in full-length tRNA
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modeling of a loop sequence inserted into the structure of human CCA-adding enzyme based on pdb-entry 1OU5. The conserved loop residue R105 forms a salt bridge to the first residue E164 of the amino acid template EDxxR in motif D
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purified recombinant monomeric native enzyme or enzyme in complex with thimerosal, sitting drop vapor diffusion method, mixing of 0.003-0.005 ml of protein solution with 0.001 ml of reservoir solution containing 100 mM sodium citrate, pH 5.6, 2.2 M ammonium sulfate, and equilibration against 0.4 ml of reservoir solution, 3 days to 3 weeks, for ligand bound enzyme crystals soaking in reservoir solution containing 0.5 mM thimerosal for 45 min, 18°C, X-ray diffraction structure determination and analysis at 3.4-3.7 A resolution, single isomorphous replacement
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Purification/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
native enzyme 11800fold by ammonium sulfate fractionation, anion exchange and hydroxylapatite chromatography, and tRNA affinity chromatography
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purified by a combination of ammonium sulfate fractionation, gel filtration, and hydrophobic interaction chromatography (NTSFII); purified by a combination of anion-exchange chromatography and hydrophobic interaction chromatography
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recombinant C-terminally His-tagged enzyme from Escherichia coli
recombinant His-tagged HD domain from Escherichia coli strain BL21 (DE3) by nickel affinity chromatography
recombinant N-terminally His-tagged mitochondrial CCase from Escherichia coli strain BL21 CodonPlus (DE3)-RP by nickel affinity chromatography and gel filtration to over 95% purity
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Cloned/COMMENTARY
ORGANISM
UNIPROT
LITERATURE
expressed in Escherichia coli
expression in Escherichia coli
mitochondrial CCase, expression as N-terminally His-tagged enzyme in Escherichia coli strain BL21 CodonPlus (DE3)-RP
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overexpression of C-terminally His-tagged enzyme in Escherichia coli
recombinant expression of the isolated His-tagged HD domain in Escherichia coli strain BL21 (DE3)
overexpression of C-terminally His-tagged enzyme in Escherichia coli
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ENGINEERING
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
E189F
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the temperature-sensitive phenotype of mutant E189F results from a reduced ability to incorporate AMP and CMP into tRNAs. This defect can be compensated for by a second-site suppressor converting residue arginine 64 to tryptophan. The R64W substitution does not alter the structure or thermal stability of the enzyme dramatically but restores catalytic activity of mutant E189F in vitro and suppresses the temperature-sensitive phenotype in vivo. Residues R64 and E189 do not interact directly, residue E189 has a role in enzyme structure and function
P295A
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kcat /Km for C74 addition is 28% of wild-type value, kcat /Km for C75 addition is 33% of wild-type value, kcat /Km for A76 addition is 1% of wild-type value
P295G
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kcat /Km for C74 addition is 94% of wild-type value, kcat /Km for C75 addition is 15% of wild-type value, kcat /Km for A76 addition is 129% of wild-type value
P295S
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kcat /Km for C74 addition is 3% of wild-type value, kcat /Km for C75 addition is 1% of wild-type value, kcat /Km for A76 addition is 1% of wild-type value
P295T
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kcat /Km for C74 addition is 36% of wild-type value, kcat /Km for C75 addition is 67% of wild-type value, kcat /Km for A76 addition is 92% of wild-type value
.R190I
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homozygous mutation identified in a patient with sideroblastic anemia with B-cell immunodeficiency, periodic fevers, and developmental delay
D139A
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mutant shows a strong reduction in the addition of the terminal A position
G143A
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similar to wild-type, mutant catalyzes the addition of the complete CCA sequence
L166S
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and T154I, compound heterozygous mutation identified in a patient with sideroblastic anemia with B-cell immunodeficiency, periodic fevers, and developmental delay
R153A
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similar to wild-type, mutant catalyzes the addition of the complete CCA sequence
T154I
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and L166S, compound heterozygous mutation identified in a patient with sideroblastic anemia with B-cell immunodeficiency, periodic fevers, and developmental delay
A75C
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as compared to wild-type enzyme the Km increases 2.7-fold from A addition to C addition, while the kcat decreased 14fold. The overall kcat/Km ratio of C addition to A addition is 0.03
D106A
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CTP-adding activity is 90% of wild-type level, ATP-adding activities is 14% of wild-type level; mutation has no effect on CCA-adding activity
D215A
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CTP-adding activity is 16% of wild-type level, ATP-adding activities is 13% of wild-type level; mutation has no effect on CCA-adding activity
E173A
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CTP-adding activity is 19% of wild-type level, ATP-adding activities is 7% of wild-type level; mutation has no effect on CCA-adding activity
E92F
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the mutant is nearly inactive for CCA addition, although tRNA binding is apparently normal
G166R
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C74-adding is 7% of wild-type activity, C75-adding is 8% of wild-type activity, A76-adding is 21% of wild-type activity
G169R
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C74-adding is 5% of wild-type activity, C75-adding is 2% of wild-type activity, A76-adding is 22% of wild-type activity
H129A
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C74-adding is 22% of wild-type activity, C75-adding is 28% of wild-type activity, A76-adding is 87% of wild-type activity
K149A
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no C74-adding activity, C75-adding is 1% of wild-type activity, A76-adding is 1% of wild-type activity
K153A
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C74-adding is 14% of wild-type activity, C75-adding is 4% of wild-type activity, A76-adding is 3% of wild-type activity
R125A
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C74-adding is 30% of wild-type activity, C75-adding is 10% of wild-type activity, A76-adding is 5% of wild-type activity
V34C
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as compared to wild-type enzyme the Km increases 1.4fold from A addition to C addition, while the kcat decreases 18fold. The overall kcat/Km ratio of C addition to A addition is 0.04
Y158A
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C74-adding is 9% of wild-type activity, C75-adding is 15% of wild-type activity, A76-adding is 7% of wild-type activity
Y90E
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the mutant is nearly wild type for CCA addition despite replacement of a conserved bulky hydrophobic residue by a carboxylate
additional information
additional information
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construction of variants bearing modifications within the body domain and bearing alterations at the extreme C-terminus of the tail domain. Mutations do not alter the overall secondary structure of the proteins to a large extent. Like wild-type, the mutant with alterations at the extreme C-terminus of the tail domain also adds a complete CCA sequence, while the mutant with modifications within the body domain and a double mutant show a complete loss of activity. A variant lacking the C-terminal nine amino acids shows a reduced rate of CCA addition in vitro when compared with the native enzyme or the mutant with alterations at the extreme C-terminus. The first five amino acids of the N-terminal signal sequence are required for efficient translocation into mitochondria. Variants lacking the first start codon show less mitochondrial import. Mutations in the mature domain reduce the localization tomitochondria and in turn enhance the translocation into chloroplasts
additional information
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construction of a conditional CCA transferase mutant that exhibits a 20% increase in doubling time when grown in the absence of inducer IPTG, and a growth rate identical to that of the wild-type strain when grown with IPTG. The cca mutation in combination with either pnpA, encoding PNPase, an enzyme with exonuclease and poly(A) polymerase activities, or rnr, encoding RNase R, an enzyme that degrades strong stem-loop structures, affects growth more than either mutation alone
additional information
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replacement of residues 100-117 in the human enzyme by the corresponding part of the Escherichia coli enzyme, positions 66-87, leading to the chimera HEH with human enzyme N-terminus, Escherichia coli flexible loop, human enzyme C-terminus. Replacement of the region in the Escherichia coli enzyme by either the human loop element, representing the reciprocal experiment, chimera EHE, or by the Bacillus stearothermophilus part, resulting in chimera EBE. Whereas the wild-type enzymes incorporate the complete CCA sequence, the chimeric enzymes EHE, HEH and EBE show a reduced activity and add only 2 C residues to the tRNA substrate. The chimeras EHE, HEH show a 45-to 145fold reduced kcat for A-incorporation. The corresponding KM values are consistent with the KM values of the loop donor enzymes
additional information
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replacement of the highly conserved residues glutamic acid, aspartic acid and arginine o f the EDxxR motif aabolishes nucleotide specificity of the enzyme
additional information
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replacement of residues 66-87 in the Escherichia coli enzyme by the Bacillus stearothermophilus loop element, resulting in chimera EBE. Whereas the wild-type enzymes incorporate the complete CCA sequence, the chimeric enzyme EBE shows a reduced activity and adds only 2 C residues to the tRNA substrate. The chimera EBE shows a reduced kcat for A-incorporation. The corresponding KM value is consistent with the KM values of the loop donor enzymes
additional information
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replacement of residues 100117 in the human enzyme by the corresponding part of the Escherichia coli enzyme, positions 6687, leading to the chimera HEH with human enzyme N-terminus, Escherichia coli flexible loop, human enzyme C-terminus. Replacement of the region in the Escherichia coli enzyme by the human loop element, representing the reciprocal experiment, chimera EHE. Whereas the wild-type enzymes incorporate the complete CCA sequence, the chimeric enzymes EHE, HEH show a reduced activity and add only 2 C residues to the tRNA substrate. The chimeras EHE, HEH show a 45- to 145fold reduced kcat for A-incorporation. The corresponding KM values are consistent with the KM values of the loop donor enzymes
additional information
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replacement of the highly conserved residues glutamic acid, aspartic acid and arginine o f the EDxxR motif aabolishes nucleotide specificity of the enzyme
additional information
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mutations near the active site can differentially affect addition of C74, C75, or A76
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APPLICATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
analysis
medicine
analysis
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a relatively short segment of the coding region for tRNA nucleotidyltransferase has a higher discriminatory potential than most established diagnostic DNA markers. The selected gene region of the tRNA nucleotidyltransferase reveals a seven- to 30fold higher distinction potential between closely related Vibrio or Aspergillus species, respectively. Even in the presence of a 1000fold excess of human genomic DNA, no unspecific amplicons are produced
analysis
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a relatively short segment of the coding region for tRNA nucleotidyltransferase has a higher discriminatory potential than most established diagnostic DNA markers. The selected gene region of the tRNA nucleotidyltransferase reveals a seven- to 30fold higher distinction potential between closely related Vibrio or Aspergillus species, respectively. Even in the presence of a 1000fold excess of human genomic DNA, no unspecific amplicons are produced
medicine
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the clinical phenotypes associated with TRNT1 mutations are largely due to impaired mitochondrial translation, resulting from defective CCA addition to mitochondrial tRNASer(AGY), and the severity of this biochemical phenotype determines the severity and tissue distribution of clinical features. TRNT1 mutations A148V and.D128G/Y173F are identified in two unrelated subjects with different clinical features. The first presented with acute lactic acidosis at 3 weeks of age and developed severe developmental delay, hypotonia, microcephaly, seizures, progressive cortical atrophy, neurosensorial deafness, sideroblastic anemia and renal Fanconi syndrome, dying at 21 months. The second presented at 3.5 years with gait ataxia, dysarthria, gross motor regression, hypotonia, ptosis and ophthalmoplegia and had abnormal signals in brainstem and dentate nucleus. In subject 1, muscle biopsy showed combined oxidative phosphorylation defects, but there was no oxidative phosphorylation deficiency in fibroblasts from either subject, despite a 10fold reduction in TRNT1 protein levels in fibroblasts of the first subject. In normal controls, TRNT1 protein levels are 10fold lower in muscle than in fibroblasts
medicine
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congenital sideroblastic anemia causing mutations in patient-derived fibroblasts do not affect subcellular localization of TRNT1 and show no gross morphological differences when compared to control cells. Both basal and maximal respiration rates are decreased in patient cells
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