Activation of the Anaerobic Ribonucleotide Reductase by S‐Adenosylmethionine

HYSCORE experiments with class III ribonucleotide reductase (RNR) provide a clear signature of S-adenosylmethionine (SAM) bound to the (4 Fe4 S) cluster of the activating enzyme β. Experiments with 2H-labeled RNR α demonstrate that, under reducing conditions, the SAM-derived adenosyl radical is the direct precursor of the key glycyl radical found in the active enzyme.