Protonation of Homocitrate and the E₁ State of Fe-Nitrogenase Studied by QM/MM Calculations.

ABSTRACT: Nitrogenase is the only enzyme that can cleave the strong triple bond in N₂, making nitrogen available for biological life. There are three isozymes of nitrogenase, differing in the composition of the active site, viz., Mo, V, and Fe-nitrogenase. Recently, the first crystal structure of Fe-nitrogenase was presented. We have performed the first combined quantum mechanical and molecular mechanical (QM/MM) study of Fe-nitrogenase. We show with QM/MM and quantum-refinement calculations that the homocitrate ligand is most likely protonated on the alcohol oxygen in the resting E₀ state. The most stable broken-symmetry (BS) states are the same as for Mo-nitrogenase, i.e., the three Noodleman BS7-type states (with a surplus of β spin on the eighth Fe ion), which maximize the

SUBMITTER: Jiang H 

PROVIDER: S-EPMC10698722 | biostudies-literature | 2023 Dec

REPOSITORIES: biostudies-literature