PMID:11248188
| Citation |
Steuber, J (2001) Na(+) translocation by bacterial NADH:quinone oxidoreductases: an extension to the complex-I family of primary redox pumps. Biochim. Biophys. Acta 1505:45-56 |
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| Abstract |
The current knowledge on the Na(+)-translocating NADH:ubiquinone oxidoreductase of the Na(+)-NQR type from Vibrio alginolyticus, and on Na(+) transport by the electrogenic NADH:Q oxidoreductases from Escherichia coli and Klebsiella pneumoniae (complex I, or NDH-I) is summarized. A general mode of redox-linked Na(+) transport by NADH:Q oxidoreductases is proposed that is based on the electrostatic attraction of a positively charged Na(+) towards a negatively charged, enzyme-bound ubisemiquinone anion in a medium of low dielectricity. A structural model of the [2Fe-2S]- and FAD-carrying NqrF subunit of the Na(+)-NQR from V. alginolyticus based on ferredoxin and ferredoxin:NADP(+) oxidoreductase suggests that a direct participation of the Fe/S center in Na(+) transport is rather unlikely. A ubisemiquinone-dependent mechanism of Na(+) translocation is proposed that results in the transport of two Na(+) ions per two electrons transferred. Whereas this stoichiometry of the pump is in accordance with in vivo determinations of Na(+) transport by the respiratory chain of V. alginolyticus, higher (Na(+) or H(+)) transport stoichiometries are expected for complex I, suggesting the presence of a second coupling site. |
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| Keywords |
Amino Acid Sequence; Bacterial Proteins/metabolism; Binding Sites; Cations, Monovalent; Cytoplasm/metabolism; Electron Transport Complex I; Escherichia coli/enzymology; Klebsiella pneumoniae/enzymology; Models, Chemical; Models, Molecular; Molecular Sequence Data; NADH, NADPH Oxidoreductases/chemistry; NADH, NADPH Oxidoreductases/metabolism; Oxidation-Reduction; Periplasm/metabolism; Quinone Reductases/metabolism; Sequence Alignment; Sodium/metabolism; Vibrio/enzymology |
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