| Primary Identifier | IPR000358 | Type | Family |
| Short Name | RNR_small_fam |
| description | Ribonucleotide reductase (RNR), also known as ribonucleoside diphosphate reductase, () [, ]catalyses the reductive synthesisof deoxyribonucleotides from their corresponding ribonucleotides:2'-deoxyribonucleoside diphosphate + oxidized thioredoxin + H2O = ribonucleoside diphosphate + reduced thioredoxinRNR provides the precursors necessary for DNA synthesis. RNRs divide into three classes on the basis of their metallocofactor usage. Class I RNRs, found in eukaryotes, bacteria, bacteriophage and viruses, use adiiron-tyrosyl radical, Class II RNRs, found in bacteria,bacteriophage, algae and archaea, use coenzyme B12(adenosylcobalamin, AdoCbl). Class III RNRs, found inanaerobic bacteria and bacteriophage, use an FeS cluster andS-adenosylmethionine to generate a glycyl radical. Manyorganisms have more than one class of RNR present in theirgenomes. Class I ribonucleotide reductase is an oligomeric enzyme composed of a large subunit (700 to 1000 residues) and a small subunit (300 to 400 residues) - class II RNRs are less complex, using the small molecule B12 in place of the small chain []. The small chain binds two iron atoms [](three Glu, one Asp, and two His areinvolved in metal binding) and contains an active site tyrosine radical. Theregions of the sequence that contain the metal-binding residues and the activesite tyrosine are conserved in ribonucleotide reductase small chain fromprokaryotes, eukaryotes and viruses.This family consist of the small subunit of class I ribonucleotide reductases. It also includes R2-like ligand-binding oxidase, which is homologous to the ribonucleotide reductase small subunit (R2), but whose function is still unknown [, ]. |
