Nitrogenase iron-molybdenum cofactor maturase NifB (NifB)

Nitrogenase iron-molybdenum cofactor maturase NifB is a crucial radical S-adenosylmethionine (SAM) enzyme found in diazotrophic bacteria and archaea. It catalyzes the first committed step in the biosynthesis of the iron-molybdenum cofactor (FeMo-co), the catalytic active site of the nitrogenase enzyme responsible for biological nitrogen fixation. NifB specifically facilitates the fusion of two [4Fe-4S] clusters into a more complex [8Fe-9S-C] core known as NifB-co, while simultaneously inserting an interstitial carbide and a sulfur atom. This enzyme is essential for the biogenesis of all three known nitrogenase types: molybdenum-dependent, vanadium-dependent, and iron-only nitrogenases. Due to its central role in converting atmospheric nitrogen into ammonia, NifB is a primary focus of synthetic biology efforts aimed at engineering nitrogen-fixing capabilities into non-diazotrophic cereal crops to reduce global reliance on synthetic fertilizers. However, the enzyme is extremely sensitive to oxygen and requires specialized auxiliary proteins for its own metallocluster assembly, presenting a major challenge for heterologous expression in plants. There are currently no therapeutic drugs that target NifB for human disease treatment, as its biological importance is primarily ecological and agricultural.

Other names

FeMo cofactor biosynthesis protein NifBRadical SAM assemblase NifBNitrogenase cofactor maturase NifBNifB-co maturase

Nitrogenase iron-molybdenum cofactor maturase NifB utilizes a radical SAM mechanism to perform the reductive coupling of two [4Fe-4S] clusters and the insertion of a carbon atom derived from the methyl group of SAM to form the [8Fe-9S-C] NifB-co cluster.