title: Dithiomethylether as a ligand in the hydrogenase h-cluster.
abstract: An X-ray crystallographic refinement of the H-cluster of [FeFe]-hydrogenase from Clostridium pasteurianum has been carried out to close-to atomic resolution and is the highest resolution [FeFe]-hydrogenase presented to date. The 1.39 A, anisotropically refined [FeFe]-hydrogenase structure provides a basis for examining the outstanding issue of the composition of the unique nonprotein dithiolate ligand of the H-cluster. In addition to influencing the electronic structure of the H-cluster, the composition of the ligand has mechanistic implications due to the potential of the bridge-head gamma-group participating in proton transfer during catalysis. In this work, sequential density functional theory optimizations of the dithiolate ligand embedded in a 3.5-3.9 A protein environment provide an unbiased approach to examining the most likely composition of the ligand. Structural, conformational, and energetic considerations indicate a preference for dithiomethylether as an H-cluster ligand and strongly disfavor the dithiomethylammonium as a catalytic base for hydrogen production.
authors.affiliation: Department of Chemistry and Biochemistry and Astrobiology Biogeocatalysis Research Center, Montana State University, Bozeman, Montana 59717, USA.
authors.forename: Arti S
authors.initials: AS
authors.lastname: Pandey
authors.forename: Travis V
authors.initials: TV
authors.lastname: Harris
authors.forename: Logan J
authors.initials: LJ
authors.lastname: Giles
authors.forename: John W
authors.initials: JW
authors.lastname: Peters
authors.forename: Robert K
authors.initials: RK
authors.lastname: Szilagyi
mesh_terms: D001665:Binding Sites; D003013:Clostridium / Q000201:enzymology; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D006864:Hydrogenase / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D008024:Ligands; D008738:Methyl Ethers / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular
chemical_list: D008024:Ligands; D008738:Methyl Ethers; C528321:dithiomethylether; D007501:Iron; D006864:Hydrogenase