EC Number   |
Natural Substrates |
|---|
   2.7.7.72 | a tRNA precursor + 2 CTP + ATP |
- |
| 2.7.7.72 | a tRNA with a 3' CCA end + 3 diphosphate |
- |
| 2.7.7.72 | deoxynucleoside triphosphate + DNAn |
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 |
| 2.7.7.72 | more |
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 |
| 2.7.7.72 | more |
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 |
| 2.7.7.72 | more |
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 |
| 2.7.7.72 | more |
the HD domain of the enzyme also exhibits 2',3'-cyclic phosphodiesterase, 2'-nucleotidase, and Ni2+-dependent phosphatase activities, overview |
| 2.7.7.72 | more |
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 |
| 2.7.7.72 | more |
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 |
