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Hydrogen activation by [NiFe]-hydrogenases

DOI: 10.1042/BST20160031 DOI Help

Authors: S. B. Carr (Research Complex at Harwell, Rutherford Appleton Laboratory) , R. M. Evans (Department of Chemistry, University of Oxford; Research Complex at Harwell) , E. J. Brooke (Department of Chemistry, University of Oxford) , S. A. M. Wehlin (Department of Chemistry, University of Oxford) , E. Nomerotskaia (Department of Chemistry, University of Oxford;Research Complex at Harwell) , F. Sargent (Division of Molecular Microbiology, School of Life Sciences, University of Dundee) , F. A. Armstrong (Department of Chemistry, University of Oxford; Research Complex at Harwell) , S. E. V. Phillips (Research Complex at Harwell, Rutherford Appleton Laboratory)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Biochemical Society Transactions , VOL 44 , PAGES 863 - 868

State: Published (Approved)
Published: June 2016
Diamond Proposal Number(s): 9306

Abstract: Hydrogenase-1 (Hyd-1) from Escherichia coli is a membrane-bound enzyme that catalyses the reversible oxidation of molecular H-2. The active site contains one Fe and one Ni atom and several conserved amino acids including an arginine (Arg(509)), which interacts with two conserved aspartate residues (Asp(118) and Asp(574)) forming an outer shell canopy over the metals. There is also a highly conserved glutamate (Glu(28)) positioned on the opposite side of the active site to the canopy. The mechanism of hydrogen activation has been dissected by site-directed mutagenesis to identify the catalytic base responsible for splitting molecular hydrogen and possible proton transfer pathways to/from the active site. Previous reported attempts to mutate residues in the canopy were unsuccessful, leading to an assumption of a purely structural role. Recent discoveries, however, suggest a catalytic requirement, for example replacing the arginine with lysine (R509K) leaves the structure virtually unchanged, but catalytic activity falls by more than 100-fold. Variants containing amino acid substitutions at either or both, aspartates retain significant activity. We now propose a new mechanism: heterolytic H-2 cleavage is via a mechanism akin to that of a frustrated Lewis pair (FLP), where H-2 is polarized by simultaneous binding to the metal(s) (the acid) and a nitrogen from Arg(509) (the base).

Journal Keywords: crystal structure; frustrated Lewis pair; hydrogenase; hydrogen splitting; mutagenesis; protein film electrochemistry

Subject Areas: Chemistry, Biology and Bio-materials, Food Science

Instruments: I02-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength) , I04-Macromolecular Crystallography