Journal Article
Proceedings of the National Academy of Sciences, vol. 115, iss. 45, 2018
Authors
Simone Raugei, Lance C. Seefeldt, Brian M. Hoffman
Abstract
Significance
This report critically evaluates the mechanism by which nitrogenase cleaves the N≡N triple bond. It assesses the thermodynamic driving force provided by the accompanying, apparently “wasteful,” reductive elimination of an H
2
, and explains how the enzyme mechanistically couples exothermic H
2
formation to endothermic triple-bond cleavage in a nearly thermoneutral equilibrium process, thereby preventing the “futile” generation of two H
2
without N
2
reduction. This evaluation rests on a critical assessment of the density functional theory flavors needed to properly treat nitrogenase, and a demonstration that to prevent spurious disruption of FeMo-co upon 4[
e
−
/H
+
] accumulation, one must employ a nitrogenase structural model that includes all residues interacting directly with FeMo-co, either via specific H-bond interactions, nonspecific electrostatic interactions, or steric confinement.
