Is Mo Involved in Hydride Binding by the Four-Electron Reduced (E_4) Intermediate of the Nitrogenase MoFe Protein?

摘要

The X-ray structure of the nitrogenase molydenum-iron (MoFe) protein reveals the active-site FeMo-cofactor (FeMo-co) to be an unprecedented [Fe_7S_9MoX; homocitrate] cluster, Figure 1, but does not define the location of substrate binding and reduction. Mo is an obvious candidate, as it is the catalytic metal in the only known inorganic metal complexes that catalytically reduce N_2. However, Fe is no less a candidate, given that it is the catalytic metal in the commercial Haber-Bosch process for NH_3 formation and that there are V and Fe nitrogenases that reduce N_2 but do not have Mo.