NifM gene product

In addition to the mechanistic role in the nitrogenase enzymatic function, Fe-protein also participates at several stages in the biosynthesis of the nitrogenase proteins. Fe-protein is essential for the production of active MoFe-protein and is involved in both the synthesis of FeMo-cofactor and its insertion into cofactor-deficient MoFe-protein (40-42). Fe-protein may also function as an activator for the expression of alternative nitrogenases (43). In turn, formation of active Fe-protein requires the nifM gene product (44, 45), which perhaps functions either in cluster insertion or in promoting the correct subunit-subunit and subunit-cofactor interactions in the Fe-protein dimer (i.e., a chaperone-type role). The significant sequence conservation observed in the Fe-protein family may reflect the structural constraints associated with these diverse aspects of Fe-protein function. 

The assembly of the molybdenum nitrogenase Fe protein involves the nifH gene and at least the nilS, nifU, and nifM gene products that are implicated in the [4Fe-4S] cluster assembly, while the assembly of MoFe protein requires at least 15 nif gene products and involves the biosynthesis of FeMo cofactor and FeMo cofactor-deficient MoFe protein in separate pathways and the insertion of FeMo cofactor into the MoFe protein. 

---