Nitrogenase catalyzes the biological reduction of dinitrogen (N2) to ammonia (NH3), a key step in the global nitrogen cycle.[1] The vanadium (V) and molybdenum (Mo) nitrogenases, two closely related members of this metalloenzyme family, share a good degree of homology both in primary sequence and in cluster topology. Both nitrogenases are binary systems comprising an adenosine triphosphate (ATP)-dependent reductase (vnfH-or nifH- ...