title: X-ray crystal structure of the Fe-only hydrogenase (CpI) from Clostridium pasteurianum to 1.8 angstrom resolution.
abstract: A three-dimensional structure for the monomeric iron-containing hydrogenase (CpI) from Clostridium pasteurianum was determined to 1.8 angstrom resolution by x-ray crystallography using multiwavelength anomalous dispersion (MAD) phasing. CpI, an enzyme that catalyzes the two-electron reduction of two protons to yield dihydrogen, was found to contain 20 gram atoms of iron per mole of protein, arranged into five distinct [Fe-S] clusters. The probable active-site cluster, previously termed the H-cluster, was found to be an unexpected arrangement of six iron atoms existing as a [4Fe-4S] cubane subcluster covalently bridged by a cysteinate thiol to a [2Fe] subcluster. The iron atoms of the [2Fe] subcluster both exist with an octahedral coordination geometry and are bridged to each other by three non-protein atoms, assigned as two sulfide atoms and one carbonyl or cyanide molecule. This structure provides insights into the mechanism of biological hydrogen activation and has broader implications for [Fe-S] cluster structure and function in biological systems.
authors.affiliation: Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322, USA. petersj@cc.usu.edu
authors.forename: J W
authors.initials: JW
authors.lastname: Peters
authors.forename: W N
authors.initials: WN
authors.lastname: Lanzilotta
authors.forename: B J
authors.initials: BJ
authors.lastname: Lemon
authors.forename: L C
authors.initials: LC
authors.lastname: Seefeldt
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002248:Carbon Monoxide / Q000737:chemistry; D020134:Catalytic Domain; D003013:Clostridium / Q000201:enzymology*; D018360:Crystallography, X-Ray; D003486:Cyanides / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D006859:Hydrogen / Q000378:metabolism; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011522:Protons; D013455:Sulfur / Q000737:chemistry
chemical_list: D003486:Cyanides; D008024:Ligands; D011522:Protons; D006639:Histidine; D013455:Sulfur; D002248:Carbon Monoxide; D006859:Hydrogen; D007501:Iron; D006864:Hydrogenase; D003545:Cysteine