title: Energy conservation by Rhodothermus marinus respiratory complex I.
abstract: A sodium ion efflux, together with a proton influx and an inside-positive DeltaPsi, was observed during NADH-respiration by Rhodothermus marinus membrane vesicles. Proton translocation was monitored by fluorescence spectroscopy and sodium ion transport by (23)Na-NMR spectroscopy. Specific inhibitors of complex I (rotenone) and of the dioxygen reductase (KCN) inhibited the proton and the sodium ion transport, but the KCN effect was totally reverted by the addition of menaquinone analogues, indicating that both transports were catalyzed by complex I. We concluded that the coupling ion of the system is the proton and that neither the catalytic reaction nor the establishment of the delta-pH are dependent on sodium, but the presence of sodium increases proton transport. Moreover, studies of NADH oxidation at different sodium concentrations and of proton and sodium transport activities allowed us to propose a model for the mechanism of complex I in which the presence of two different energy coupling sites is suggested.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República EAN, Oeiras, Portugal.
authors.forename: Ana P
authors.initials: AP
authors.lastname: Batista
authors.forename: Andreia S
authors.initials: AS
authors.lastname: Fernandes
authors.forename: Ricardo O
authors.initials: RO
authors.lastname: Louro
authors.forename: Julia
authors.initials: J
authors.lastname: Steuber
authors.forename: Manuela M
authors.initials: MM
authors.lastname: Pereira
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004735:Energy Transfer; D017136:Ion Transport / Q000187:drug effects; D009682:Magnetic Resonance Spectroscopy; D009243:NAD / Q000378:metabolism; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010101:Oxygen Consumption; D011190:Potassium Cyanide / Q000494:pharmacology; D018892:Proton-Motive Force; D011522:Protons; D045245:Rhodothermus / Q000378:metabolism*; D012402:Rotenone / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D001426:Bacterial Proteins; D011522:Protons; D012402:Rotenone; D009243:NAD; D012964:Sodium; D010088:Oxidoreductases; D042967:Electron Transport Complex I; D011190:Potassium Cyanide; D010100:Oxygen