This family contains several NIF (B, Y and X) proteins which are iron-molybdenum cofactors (FeMo-co) in the dinitrogenase enzyme which catalyses the reduction of dinitrogen to ammonium. Dinitrogenase is a hetero-tetrameric (alpha(2)beta(2)) enzyme which contains the iron-molybdenum cofactor (FeMo-co) at its active site [1].

1: Cloning and mutational analysis of the gamma gene from Azotobacter vinelandii defines a new family of proteins capable of metallocluster binding and protein stabilization. Rubio LM, Rangaraj P, Homer MJ, Roberts GP, Ludden PW; J Biol Chem 2002;277:14299-14305. PMID:11823455