title: Electron paramagnetic resonance studies of the iron-sulfur centers from complex I of Rhodothermus marinus.
abstract: Rhodothermus marinus, a thermohalophilic gram negative bacterium, contains a type I NADH/quinone oxidoreductase (complex I). Its purification was optimized, yielding large amounts of pure and active protein. Furthermore, the stoichiometry of NADH oxidation and quinone reduction was shown to be 1:1. The large amounts of protein enabled a thorough characterization by electron paramagnetic resonance (EPR) spectroscopy at different temperatures and microwave powers, using NADH, NADPH, and dithionite as reducing agents. A minimum of two [2Fe-2S](2+/1+) and four [4Fe-4S](2+/1+) centers were observed in the purified complex. Redox titrations monitored by EPR spectroscopy made possible the determination of the reduction potentials of the iron-sulfur centers; with the exception of one of the [4Fe-4S](2+/1+) centers, which has a lower reduction potential, all the other centers have reduction potentials of -240 +/- 20 mV, pH 7.5.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República, Apartado 127, 2784-505 Oeiras, Portugal.
authors.forename: Andreia S
authors.initials: AS
authors.lastname: Fernandes
authors.forename: Filipa L
authors.initials: FL
authors.lastname: Sousa
authors.forename: Miguel
authors.initials: M
authors.lastname: Teixeira
authors.forename: Manuela M
authors.initials: MM
authors.lastname: Pereira
mesh_terms: D001665:Binding Sites; D004578:Electron Spin Resonance Spectroscopy; D042967:Electron Transport Complex I / Q000737:chemistry* / Q000302:isolation & purification; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000302:isolation & purification; D010084:Oxidation-Reduction; D045245:Rhodothermus / Q000201:enzymology*; D013455:Sulfur / Q000737:chemistry* / Q000378:metabolism
chemical_list: D007506:Iron-Sulfur Proteins; D013455:Sulfur; D007501:Iron; D042967:Electron Transport Complex I