Na + translocation by bacterial NADH:quinone oxidoreductases: an extension to the complex-I family of primary redox pumps

• Published in: BBA - Bioenergetics Vol. 1505; no. 1; pp. 45 - 56
• Main Author: Steuber, Julia
• Format: Book Review Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-05-2001
• Subjects: Amino Acid Sequence; Bacterial Proteins - metabolism; Binding Sites; Cations, Monovalent; Complex I; Cytoplasm - metabolism; Electron Transport Complex I; Escherichia coli - enzymology; Klebsiella pneumoniae; Klebsiella pneumoniae - enzymology; Models, Chemical; Models, Molecular; Molecular Sequence Data; Na + transport; Na +/H + antiporter; NADH; NADH, NADPH Oxidoreductases - chemistry; NADH, NADPH Oxidoreductases - metabolism; Oxidation-Reduction; Periplasm - metabolism; Quinone Reductases - metabolism; Sequence Alignment; Sodium - metabolism; Ubiquinone; Vibrio - enzymology; Vibrio alginolyticus; NADH; Ubiquinone; Na +/H + antiporter; Complex I; Vibrio alginolyticus; Klebsiella pneumoniae; Na + transport
• ISSN: 0005-2728; 0006-3002; 1879-2650
• DOI: 10.1016/S0005-2728(00)00276-0

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.