title: A low-spin iron with CN and CO as intrinsic ligands forms the core of the active site in [Fe]-hydrogenases.
abstract: In this report the first high-quality infrared spectra of [Fe]-hydrogenase are presented. Analyses of these spectra obtained under a variety of redox conditions strongly indicate that [Fe]-hydrogenases contain a low-spin Fe ion in the active site with one CN- group and one CO molecule as intrinsic, non-protein ligands. When in the ferric state, the presence of such an ion can explain the enigmatic EPR properties (the rhombic 2.10 signal) of the active, oxidised enzyme. To account for other, well-characterised properties of the active site, we propose that the active site of [Fe]-hydrogenases consists of this low-spin Fe ion bound to an unusual [4Fe-4S] cluster via bridges with sulphur atoms.
authors.affiliation: E. C. Slater Institute, Biochemistry, University of Amsterdam, The Netherlands.
authors.forename: A J
authors.initials: AJ
authors.lastname: Pierik
authors.forename: M
authors.initials: M
authors.lastname: Hulstein
authors.forename: W R
authors.initials: WR
authors.lastname: Hagen
authors.forename: S P
authors.initials: SP
authors.lastname: Albracht
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D016969:Desulfovibrio vulgaris / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D006859:Hydrogen / Q000737:chemistry; D006864:Hydrogenase / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D015394:Molecular Structure; D019159:Nonheme Iron Proteins / Q000737:chemistry; D010084:Oxidation-Reduction; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D001426:Bacterial Proteins; D007506:Iron-Sulfur Proteins; D019159:Nonheme Iron Proteins; D006859:Hydrogen; C043296:nickel-iron hydrogenase; D006864:Hydrogenase