The Crystal Structure of the Nitrogenase MoFe Protein from Clostridium Pasteurianum

Abstract

Mo-dependent nitrogenases catalyze reduction of dinitrogen through the activity of a complex of two easily separated components known as the MoFe-protein (component 1) and the Fe-protein (component 2). The latter is a homodimer, M_r= 60–70,000, which binds a single Fe₄S₄ cluster symmetrically between the subunits. The structure of Av2, the Fe-protein from Azotobacter vinelandii, has been determined to 2.9Å resolution by Georgiadis et al. (1992). MoFe-protein is an α₂β₂ tetramer, M_r= 220–230,000, which binds two Mo atoms and 30 Fe atoms in the form of four large metal-sulfur clusters of two types; two clusters of each type are present per tetramer, one of each per αβ dimer.