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malfunction
wild-type plants exposed to a low concentration of an RNR inhibitor, hydroxyurea, produce chlorotic leaves without growth retardation, reminiscent of v3 and st1 mutants. Upon insufficient activity of RNR, plastid DNA synthesis is preferentially arrested to allow nuclear genome replication in developing leaves, leading to continuous plant growth
metabolism
constitutive ribonucleotide reductase activity ensures stable and balanced dNTP production, which is essential for de novo DNA synthesis. The enzyme is responsible for the rate-limiting step of de novo DNA synthesis
metabolism
constitutive RNR activity ensures stable and balanced dNTP production, which is essential for de novo DNA synthesis. The enzyme is responsible for the rate-limiting step of de novo DNA synthesis
metabolism
key enzyme in DNA synthesis and cell growth control
metabolism
provides the precursors necessary for DNA synthesis. Constitutive ribonucleotide reductase activity ensures stable and balanced dNTP production, which is essential for de novo DNA synthesis. The enzyme is responsible for the rate-limiting step of de novo DNA synthesis
metabolism
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the enzyme maintains balanced pools of deoxyribonucleotide substrates for DNA replication by converting ribonucleoside diphosphates to 2'-deoxyribonucleoside diphosphates
metabolism
the enzyme maintains balanced pools of deoxyribonucleotide substrates for DNA replication by converting ribonucleoside diphosphates to 2'-deoxyribonucleoside diphosphates
metabolism
the reduction of ribonucleoside diphosphate to deoxyribonucleoside diphosphate is the rate-limiting step in dNTP production
physiological function
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hp53R2 possibly plays a regulatory role in iron assimilation
physiological function
RNR is an essential enzyme that provides dNTPs for DNA replication and repair, AtRNR2A induction is likely required for the replicative stress checkpoint. Individual RNR2-like catalytic subunit genes participate in unique aspects of the cellular response to DNA damage in Arabidopsis thaliana
physiological function
RNR is an essential enzyme that provides dNTPs for DNA replication and repair, TSO2 and E2Fa are likely required for the DNA damage response. Individual RNR2-like catalytic subunit genes participate in unique aspects of the cellular response to DNA damage in Arabidopsis thaliana
physiological function
RNR is an essential enzyme that provides dNTPs for DNA replication and repair. Individual RNR2-like catalytic subunit genes participate in unique aspects of the cellular response to DNA damage in Arabidopsis thaliana
physiological function
RNR regulates the rate of deoxyribonucleotide production for DNA synthesis and repair. Rice virescent3 and stripe1 encoding the large and small subunits of ribonucleotide reductase are required for chloroplast biogenesis during early leaf development
physiological function
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the enzyme is involved in DNA replication and damage repair, respectively
physiological function
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class Ib RNR converts nucleoside 5'-diphosphates to deoxynucleoside 5'-diphosphates in iron-limited and oxidative stress conditions
physiological function
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Escherichia coli class Ib RNR converts nucleoside 5'-diphosphates to deoxynucleoside 5'-diphosphates and is expressed under iron-limited and oxidative stress conditions
physiological function
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ribonucleoside diphosphate reductase is an essential enzyme for the biosynthesis of the four dNTP in all living cells
physiological function
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RNRs catalyze the conversion of nucleotides UDP, ADP, GDP, and CDP to deoxynucleotides, providing the monomeric building blocks required for DNA replication and repair
physiological function
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role of RNRs during infection of macrophages and epithelial cells, overview. Class Ia to be mainly responsible for deoxyribonucleotide production during invasion and proliferation inside macrophages and epithelial cells, while class Ib RNR is not. Class Ib RNR may contribute to deoxyribonucleotide synthesis by means of both an NrdR and a Fur-dependent derepression of nrdHIEF due to hydrogen peroxide production and DNA damage associated with the oxidative burst, thus helping to overcome the host defenses
physiological function
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the allosterically regulated enzyme is responsible for the reduction of all four ribonucleotides to their corresponding deoxyribonucleotides, dNTPs, which are the building blocks of DNA. This reaction involves a free radical, the activity of RNR regulates the cellular levels of the dNTP pool, ensuring that precise DNA replication and repair occurs
physiological function
the class Ib ribonucleotide reductase can initiate reduction of nucleotides to deoxynucleotides with either a MnIII 2-tyrosyl radical or a FeIII 2-tyrosyl radical cofactor in the NrdF subunit. Whereas FeIII 2-tyrosyl radical can self-assemble from FeII 2-NrdF and O2, activation of MnII 2-NrdF requires a reduced flavoprotein, NrdI, proposed to form the oxidant for cofactor assembly by reduction of O2
physiological function
a conserved cluster of charged residues, including Lys95, Glu98, Glu-05, and Glu174, at the interface may function as an ionic lock for small subunit M2 homodimer. The transfection of the wild-type small subunit M2 but not the K95E mutant rescues theG1/S phase cell cycle arrest and cell growth inhibition caused by the siRNA knockdown of M2
physiological function
in nontransformed cells only during quiescence, isoform p53R2 is required for maintenance of mitochondrial DNA and for optimal DNA repair after UV damage
physiological function
isoform NrdEF is induced during H2O2 stress. Induction is mediated by the inactivation of Fur, an iron-dependent repressor. NrdEF supports cell replication in iron-depleted cells. Iron binds to NrdF when it is expressed in iron-rich cells, but NrdEF is functional only in cells that are both iron-depleted and manganese-rich
physiological function
the properties of tyrosyl radical metalloprotein NrdF loaded with iron or manganese are in general similar for interaction with catalyitc subunit NrdE and flavodoxin protein NrdI. The enzyme activity in presence of manganese is approximately an order of magnitude higher than that in presence of iron in the presence of the class specific physiological reductant NrdH
physiological function
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the ribonucleotide reductase response to DNA damage does not operate similarly across the cell cycle at either the transcript or the protein level. Ribonucleotide reductase subunit mRNA levels are comparably low in both damaged and undamaged G1 cells and highly induced in damaged S/G2 cells. Transcript numbers becomes correlated with both protein levels and localization only upon DNA damage in a cell cycle-dependent manner. The differential ribonucleotide reductase response to DNA damage correlates with variable Mec1 kinase activity in the cell cycle in single cells. The transcription of ribonucleotide reductase genes is noisy and non-Poissonian in nature
physiological function
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the enzyme catalyzes the reduction of ribonucleotides to the corresponding deoxyribonucleotides, which are used as building blocks for DNA replication and repair
physiological function
the enzyme converts ribonucleotides to deoxyribonucleotides, a reaction that is essential for DNA biosynthesis and repair
physiological function
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class Ib RNR converts nucleoside 5'-diphosphates to deoxynucleoside 5'-diphosphates in iron-limited and oxidative stress conditions
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physiological function
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RNRs catalyze the conversion of nucleotides UDP, ADP, GDP, and CDP to deoxynucleotides, providing the monomeric building blocks required for DNA replication and repair
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physiological function
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ribonucleoside diphosphate reductase is an essential enzyme for the biosynthesis of the four dNTP in all living cells
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physiological function
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the properties of tyrosyl radical metalloprotein NrdF loaded with iron or manganese are in general similar for interaction with catalyitc subunit NrdE and flavodoxin protein NrdI. The enzyme activity in presence of manganese is approximately an order of magnitude higher than that in presence of iron in the presence of the class specific physiological reductant NrdH
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additional information
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as the pH is elevated, the rate-determining step of RNR can be altered from a conformational change to proton-coupled electron transfer, and the altered driving force for F3Y oxidation, by residues adjacent to it in the pathway, is responsible for this change
additional information
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RNR and the dNTP-synthesizing complex are closely linked to the replication proteins or replisome at the replication fork, coordinated organization of NrdB protein, and consequently RNR protein, with other replication proteins. NrdB is present in nucleoid-associated clusters during the replication period. These clusters disappear after replication ends. Replication hyperstructure model, overview
additional information
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RNRs are allosterically regulated on two levels, overall activity and substrate specificity. The substrate specificity is regulated by the binding of dNTPs to the specificity site, ATP and dATP upregulate the reduction of CDP and UDP, whereas dTTP upregulates GDP reduction and dGTP increases the rate of ADP reduction. This regulation is essential to maintain balanced dNTP pools for DNA synthesis and repair
additional information
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RNRs are allosterically regulated on two levels, overall activity and substrate specificity. The substrate specificity is regulated by the binding of dNTPs to the specificity site, ATP and dATP upregulate the reduction of CDP and UDP, whereas dTTP upregulates GDP reduction and dGTP increases the rate of ADP reduction. This regulation is essential to maintain balanced dNTP pools for DNA synthesis and repair
additional information
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RNRs are allosterically regulated on two levels, overall activity and substrate specificity. The substrate specificity is regulated by the binding of dNTPs to the specificity site, ATP and dATP upregulate the reduction of CDP and UDP, whereas dTTP upregulates GDP reduction and dGTP increases the rate of ADP reduction. This regulation is essential to maintain balanced dNTP pools for DNA synthesis and repair. The overall activity is regulated by the binding of dATP (inhibition) or ATP (stimulation) to the socalled activity site in the ATP cone domain of the alpha2 subunit of RNRs from class Ia
additional information
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RR is regulated transcriptionally and allosterically. RR activity is also controlled by subunit RR2 levels
additional information
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structural basis for substrate selection, RR activity is lowest at high dATP concentrations when the hexamer population is high, egulation of RR by dATPinduced oligomerization, overview. RR is regulated transcriptionally and allosterically. RR is further regulated by subunit localization and by its protein inhibitor Sml1
additional information
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the reaction of class I RNRs involves tyrosyl or cysteinyl radicals and requires aerobic conditions, while for class II RNRs the reaction involves deoxyadenosyl or cysteinyl radicals and is independent of oxygen
additional information
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the reaction of class I RNRs involves tyrosyl or cysteinyl radicals and requires aerobic conditions, while for class II RNRs the reaction involves deoxyadenosyl or cysteinyl radicals and is independent of oxygen
additional information
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the reaction of class I RNRs involves tyrosyl or cysteinyl radicals and requires aerobic conditions, while for class II RNRs the reaction involves deoxyadenosyl or cysteinyl radicals and is independent of oxygen. The thiyl radical in class II RNR is believed to be generated directly at the active site using the cofactor 5'-deoxyadenosylcobalamin
additional information
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the reaction of class Ia RNRs involves tyrosyl or cysteinyl radicals and requires aerobic conditions
additional information
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the reaction of class Ia RNRs involves tyrosyl or cysteinyl radicals and requires aerobic conditions
additional information
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transcriptional regulation of RNR classes as well as their differential function during infection of macrophage and epithelial cells, overview
additional information
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comparative analyses of ribonucleotide reductase homologs. Results of homology modeling studies indicate that most of the bifidobacteria-specific conserved signature indels are located within the surface loops of the ribonucleotide reductases, and of these, a large 43 amino acid insert in the class III ribonucleotide reductase homolog forms an extension of the allosteric regulatory site known to be essential for protein function. Preliminary docking studies suggest that this large conserved signature indels may be playing a role in enhancing the stability of the RNR dimer complex
additional information
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comparative analyses of ribonucleotide reductase homologs. Results of homology modeling studies indicate that most of the bifidobacteria-specific conserved signature indels are located within the surface loops of the ribonucleotide reductases, and of these, a large 43 amino acid insert in the class III ribonucleotide reductase homolog forms an extension of the allosteric regulatory site known to be essential for protein function. Preliminary docking studies suggest that this large conserved signature indels may be playing a role in enhancing the stability of the RNR dimer complex
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