This family represents the C-terminus (approximately 80 residues) of a number of bacterial Mo-dependent nitrogenases. These are involved in nitrogen fixation in cyanobacteria [1]. Note that many family members are hypothetical proteins.

1: A second nitrogenase in vegetative cells of a heterocyst-forming cyanobacterium. Thiel T, Lyons EM, Erker JC, Ernst A; Proc Natl Acad Sci U S A 1995;92:9358-9362. PMID:7568132