Nitrogenase

Nitrogenase catalyzes the enzymatic reduction of atmospheric dinitrogen to ammonia during the process of biological nitrogen fixation. Nitrogenase consists of two component metalloproteins, the iron (Fe-) protein and the molybdenum-iron (MoFe-) protein, that together mediate the ATP-hydrolysis–dependent reduction of substrates to products. Crystallographic studies have established the structures of the component proteins and the associated complex metallocenters of nitrogenase, including the iron-molybdenum cofactor that provides the active site for substrate reduction and the P-cluster that participates in electron transfer between the Fe-protein and MoFe-protein. Striking parallels are evident in the interaction of the nucleotides with the Fe-protein and with a broad class of nucleotide-binding proteins involved in signal and energy transduction processes. Together with kinetic, spectroscopic, and synthetic model compound studies, these structures provide a framework for addressing the mechanism of substrate reduction by nitrogenase.