Ribonucleoside-triphosphate reductase, anaerobic (IPR012833)

Short name: NrdD

Overlapping homologous superfamilies


Family relationships



This entry represents anaerobic, class III ribonucleotide reductase. The mechanism of the enzyme involves a glycine-centred radical [PMID: 10066165], a C-terminal zinc binding site [PMID: 12655046], and a set of conserved active site cysteines and asparagines [PMID: 11526118]. This enzyme requires an activating component, NrdG, a radical-SAM domain containing enzyme (IPR012837). Together the two form an alpha-2/beta-2 heterodimer.

Ribonucleotide reductase (RNR) catalyzes the reductive synthesis of deoxyribonucleotides from their corresponding ribonucleotides. It provides the precursors necessary for DNA synthesis. RNRs are separated into three classes based on their metallocofactor usage. Class I RNRs, found in eukaryotes, bacteria, and bacteriophage, use a diiron-tyrosyl radical. Class II RNRs, found in bacteria, bacteriophage, algae and archaea, use coenzyme B12 (adenosylcobalamin, AdoCbl). Class III RNRs, found in strict or facultative anaerobic bacteria, bacteriophage, and archaea, use an FeS cluster and S-adenosylmethionine to generate a glycyl radical [PMID: 15158709]. Many organisms have more than one class of RNR present in their genomes. All three RNRs have a ten-stranded alpha-beta barrel domain that is structurally similar to the domain of PFL (pyruvate formate lyase) [PMID: 10574800]. The class III enzyme from phage T4 consists of two subunits, this model covers the larger subunit which contains the active and allosteric sites.

GO terms

Biological Process

GO:0006260 DNA replication
GO:0055114 oxidation-reduction process

Molecular Function

GO:0016491 oxidoreductase activity
GO:0008998 ribonucleoside-triphosphate reductase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.