Nitrogenase is a key enzyme in the biological nitrogen cycle that catalyzes the reduction of atmospheric nitrogen to ammonia. It has a complex multi-domain structure consisting of a tetrameric central structure (MoFe protein) containing two active sites and their corresponding iron-molybdenum cofactors (FeMoCo), as well as two dimeric Fe proteins, which deliver electrons to the MoFe protein via an ATP-dependent process. Electrons are shuttled to FeMoCo via an [8Fe7S] P-cluster on the outer edge of the MoFe protein. Recent work by Seefeldt and co-workers has found evidence for modulation of nitrogenase activity from negative cooperativity in large-scale motions of the Fe protein (Proc. Natl. Acad. Sci. 2016, 113, E5783-E5791) as well as by motion of several aromatic residues located between the P-cluster and FeMoCo (Biochemistry 2015, 54, 2456-2462). We have used microsecond-scale classical molecular dynamics simulations of the nitrogenase complex to identify key large-scale motions in the complex and correlate them with changes in local structure and electron transfer. We have also further examined key structures and states identified with the classical simulations using DFT and QM/MM calculations.

Modulation of electron transfer in nitrogenase

254th National Meeting (2017)

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