Identification of nitrogenase cofactor biosynthetic precursors on NifB

CBGP researchers, in collaboration with the group of David Britt at the University of California-Davis, show that the nitrogenase iron-molybdenum cofactor (FeMo-co) maturase NifB carries three [4Fe-4S] clusters. In addition to the catalytic SAM binding cluster, NifB carries two auxiliary [4Fe-4S] clusters proposed to serve as substrates for the biosynthesis of the Fe₈S₉C core of FeMo-co. Spectroscopic evidence indicates coordination of a SAM molecule (acting as methyl donor) to one of the auxiliary clusters, as well as N coordination to at least one of the auxiliary clusters, which permits a mechanism to release the FeS cluster product through protonation. This analysis represents concise and novel data to understand the mechanism of synthesis of the Fe₈S₉C core of FeMo-co.