Energy conservation by Rhodothermus marinus respiratory complex I |
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Authors: | Ana P. Batista Andreia S. Fernandes Ricardo O. Louro Manuela M. Pereira |
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Affiliation: | a Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República EAN, 2780-157 Oeiras, Portugal b Biochemisches Institut, Universität Zürich, CH-8057 Zürich, Switzerland |
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Abstract: | A sodium ion efflux, together with a proton influx and an inside-positive ΔΨ, was observed during NADH-respiration by Rhodothermus marinus membrane vesicles. Proton translocation was monitored by fluorescence spectroscopy and sodium ion transport by 23Na-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. |
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Keywords: | ACMA, 9-amino-6-chloro-2-methoxyacridine CCCP, carbonyl cyanide m-chlorophenyl hydrazone DDM, n-dodecyl-β-D-maltoside DMN, 2,3-Dimethyl-1,4-naphthoquinone Dy(PPPi)27&minus , dysprosium (III) tripolyphosphate HiPIP, high-potential iron-sulphur protein Menadione, 2-methyl-1,4-naphthoquinone NQ, 1,4-Naphthoquinone oxonol V, 1,5-Bis(3-phenyl-5-oxoisoxazol-4-yl) pentamethine oxonol TEMPO, 2,2,6,6-tetramethyl-piperidine-1-oxyl Tm(DOTP)5&minus , thulium (III) 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylenephosphate) ΔΨ, transmembrane difference of electric potential |
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