PROTEIN-COMPONENT COMPLEX-FORMATION AND ADENOSINE-TRIPHOSPHATE HYDROLYSIS IN NITROGENASE

Substrate reduction by nitrogenase requires efficient electron transfer between the unique donor, Fe-protein, and the site of substrate binding, the MoFe-protein. The unidirectional transfer of electrons between components is accomplished by an elegant switching mechanism which is driven by the hydrolysis of MgATP. Specific ionic interactions at the surface of the two components leads to the formation of a functional complex. The ionic residues involved have been identified by chemical modification and mutagenesis studies. The correlation of the altered properties to the effects on ATP turnover and substrate reduction have been assessed in kinetic experiments. Based upon the recently determined three-dimensional structures of the components, a model for docking and ATP hydrolysis is presented.