NifV

NifV is a gene found in some nitrogen-fixing bacteria that encodes a homocitrate synthase involved in the maturation of the Mo-containing nitrogenase cofactor, known as FeMo-co. In organisms that require it, NifV provides homocitrate, a key ligand for molybdenum in the FeMo-cofactor, enabling proper assembly and function of the MoFe nitrogenase enzyme complex.

The encoded enzyme catalyzes the formation of homocitrate from substrates such as acetyl-CoA and 2-oxoglutarate, a reaction analogous to other homocitrate synthases. The produced homocitrate is then incorporated into FeMo-co during cofactor biosynthesis, a process coordinated with other maturation proteins in the nif gene cluster, such as NifB and NifEN, to yield a catalytically competent Mo-nitrogenase.

Distribution and significance vary among diazotrophs. NifV is not universally present in all nitrogen-fixing organisms; some species lack the gene and depend on alternative assembly pathways or exogenous homocitrate for Mo-nitrogenase maturation. In organisms that require NifV, its activity is important for efficient nitrogen fixation under conditions where endogenous homocitrate synthesis supports FeMo-cofactor assembly.

Evolution and regulation of nifV are linked to the broader nif gene cluster governing nitrogenase biosynthesis. Expression is typically regulated by nitrogen availability and metal cofactor status, aligning homocitrate production with the synthesis of nitrogenase components. Understanding NifV informs efforts to engineer nitrogen fixation in non-native hosts by highlighting a potential bottleneck in cofactor maturation.