BIOSYNTHESIS OF THE IRON-MOLYBDENUM COFACTOR OF NITROGENASE

The iron-molybdenum cofactor (FeMo-co) of nitrogenase is a unique moly bdenum-containing prosthetic group that has been proposed to form an i ntegral part of the active site of dinitrogenase. In Klebsiella pneumo niae, at least six nif (nitrogen fixation) gene products are required for the biosynthesis of FeMo-co, including NIFB, NIFNE, NIFH, NIFQ, an d NIFV. An in vitro system for the synthesis of FeMo-co, which require s MgATP, molybdate, homocitrate, and at least the products of nifN, E, B, and H, has provided an enzymatic assay for the purification of man y of the gene products required for FeMo-co biosynthesis. Although the structure of the cofactor has been solved recently, much about the bi osynthetic pathway remains unknown. This article reviews what is known about the various components required for FeMo-co biosynthesis.