Structure and Function of Nitrogenase

Abstract

This chapter discusses the structures of the metal centers and polypeptide chains of the nitrogenase proteins based on the crystallographic structures of both the Fe-protein and the MoFe protein that have been determined at Caltech. The discussion is presented in the context of the nitrogenase protein structures. The two nitrogenase proteins, Fe-protein and MoFe-protein, are composed of a total of three different types of subunits and contain three different types of metal centers. The properties of the nitrogenase proteins have been discussed in the chapter. To distinguish the two nitrogenase proteins, isolated from different bacterial sources, the MoFe-protein and Fe-protein are designated as components "1" and "2," respectively, preceded by a two-letter abbreviation of the source species and genus—that is, Av1 is MoFe-protein isolated from Azotobacter vinelandii and Cp2 is Fe-protein isolated from Clostridium pasteurianum, etc. In addition to the mechanistic role in the nitrogenase enzymatic function, Fe-protein also participates at several stages in the biosynthesis of the nitrogenase proteins. The chapter explains the nitrogenase mechanism from the viewpoint of an electron traveling through the system. The Haber–Bosch process utilizes an iron catalyst to accelerate the rate of ammonia formation from dinitrogen and hydrogen.

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