title: Spectroscopic characterization of the nickel and iron-sulphur clusters of hydrogenase from the purple photosynthetic bacterium Thiocapsa roseopersicina. 1. Electron spin resonance spectroscopy.
abstract: The thermostable hydrogenase from Thiocapsa roseopersicina was examined by low-temperature ESR spectroscopy. Two types of signals were detected, from an oxidized iron-sulphur cluster and a nickel centre (Ni-A). In the oxidized protein additional signals were observed due to spin-spin interaction between the two paramagnetic centres. This interaction could be reversibly abolished by reduction to a redox potential below 105 mV. This implies that an additional redox centre is involved in the interaction, for which an Fe3+ ion is suggested. Reduction with hydrogen induced a second type of nickel ESR signal (Ni-C), corresponding to an intermediate redox state seen in other nickel hydrogenases. The Ni-C species was light-sensitive at cryogenic temperatures. At temperatures near to 4.2 K the Ni-C signal showed evidence of interaction with another paramagnetic centre, presumably a second iron-sulphur cluster. On reoxidation a signal due to a third Ni(III) species, Ni-B, increased in amplitude. These results establish that metal centres in the hydrogenase from T. roseopersicina are closely similar to those of the well-studied hydrogenase from Chromatium vinosum.
authors.affiliation: Department of Biochemistry, King's College, London, England.
authors.forename: R
authors.initials: R
authors.lastname: Cammack
authors.forename: C
authors.initials: C
authors.lastname: Bagyinka
authors.forename: K L
authors.initials: KL
authors.lastname: Kovacs
mesh_terms: D002841:Chromatiaceae / Q000201:enzymology*; D002844:Chromatium / Q000201:enzymology; D003080:Cold Temperature; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D006864:Hydrogenase / Q000032:analysis*; D007506:Iron-Sulfur Proteins / Q000032:analysis*; D008667:Metalloproteins / Q000032:analysis*; D009532:Nickel; D010084:Oxidation-Reduction
chemical_list: D007506:Iron-Sulfur Proteins; D008667:Metalloproteins; D009532:Nickel; C043296:nickel-iron hydrogenase; D006864:Hydrogenase