Structural Basis for Superoxide Activation of <i>Flavobacterium johnsoniae</i> Class I Ribonucleotide Reductase and for Radical Initiation by Its Dimanganese Cofactor

Abstract

cluster. Relative to the positions of the radical tyrosines in the Ia/b proteins, the unreactive Tyr 104 of Fj β is held away from the cofactor by a hydrogen bond with a subclass-d-specific Thr residue. Structural comparisons, considered with its uniquely simple mode of activation, suggest that the Id protein might most closely resemble the primordial RNR-β.