Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides in all organisms.  The b2 subunit (NrdF) of the E. coli and B. subtilis class Ib RNRs contain a dimanganese (III)-tyrosyl radical (Y�) cofactor essential for activity.  Our studies have demonstrated that NrdI, a flavodoxin with flavin oxidase-like activity, is required for cluster biosynthesis in both cases.  The results of stopped flow Vis spectroscopy and rapid freeze quench (RFQ) EPR experiments mixing NrdI�NrdF (MnII2)with O2 will be presented for the B. subtilis NrdF.  These studies and a recent structure of the B. subtilis MnII2NrdF, suggest the nature of the oxidant and intermediates involved in tyrosine oxidation. A mechanistic model will be presented.  The importance in vivo of controlling metal delivery (iron vs  manganese) and avoiding protein mismetallation will be discussed.

Mechanism of assembly of the dimanganese-tyrosyl radical cofactor of class Ib ribonucleotide reductases

243rd National Meeting (2012)

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