Nitrogenase catalyzes the multi-electron/proton reduction of N2 to two NH3 in a reaction that is coupled to the hydrolysis of ATP.  Two component proteins, called the Fe protein and the MoFe protein, act together to achieve N2 reduction, utilizing three different FeS cofactors including a [4Fe-4S] cluster, an [8Fe-7S] or P cluster, and a [7Fe-9S-1Mo-X-R-homocitrate] or FeMo-cofactor.  We will report progress in understanding the order of transfer of electrons among these three cofactors and the roles of ATP hydrolysis in activating each electron transfer step.  Further, evidence will be presented showing that single amino acid substitutions within the MoFe protein can partially mimic the roles of ATP and Fe protein, allowing the MoFe protein to reduce substrates in the absence of the Fe protein using Eu(II)-ligand as a reductant.  Significant progress has also been made in understanding how N2 binds and is reduced at the active site FeMo-cofactor.

Nitrogenase electron transfer and substrate reduction

243rd National Meeting (2012)

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