Ribonucleotide Reductase: Difference between revisions

The conversion from ribonucleotides to deoxyribonucleotides is a radically-based reaction. Organic free radicals are stored by RNR until they are needed for catalysis. Class I ribonucleotide reductase produces the stable radical, tyrosyl, through the dinuclear iron center of the subunit. This class is the most studied and most well known enzyme that is a part of the RNR family. It is composed of two subunits, alpha and beta, that are homodimeric. The alpha subunit contains the active site and two allosteric sites. The active site contains a catalytic subunit, and the allosteric sites are used for regulation, enzyme activity, and substrate specificity. The beta portion contains the metal cofactor that initiates reduction. Class I is subdivided into three more enzymes that are class Ia, Ib, and Ic. Class one is split even further because it is depending on the specific type of metal center that is needed for protein radical. All three classes share the same function for the beta subunit which is synthesizing the radical which is transferred using a radical transfer pathway. Class Ia requires a di-iron center as the nrdAB gene codes for this enzyme. Class Ib uses either a di-manganese center or a di-ferric center. This specific class differs from the other class I enzymes by lacking the active site located at the N-terminal portion of the protein. This enzyme is coded by the gene nrdHIEF Class Ic is encoded by the nrdAB gene, and it requires a manganese-iron center. Class I and its subdivision are all aerobic and require oxygen for the generation of the radical. This enzyme can be found in eukaryotes, archaea, eubacteria, and bacteriophages.