title: Localization of ubiquinone-8 in the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae.
abstract: Na(+) is the second major coupling ion at membranes after protons, and many pathogenic bacteria use the sodium-motive force to their advantage. A prominent example is Vibrio cholerae, which relies on the Na(+)-pumping NADH:quinone oxidoreductase (Na(+)-NQR) as the first complex in its respiratory chain. The Na(+)-NQR is a multisubunit, membrane-embedded NADH dehydrogenase that oxidizes NADH and reduces quinone to quinol. Existing models describing redox-driven Na(+) translocation by the Na(+)-NQR are based on the assumption that the pump contains four flavins and one FeS cluster. Here we show that the large, peripheral NqrA subunit of the Na(+)-NQR binds one molecule of ubiquinone-8. Investigations of the dynamic interaction of NqrA with quinones by surface plasmon resonance and saturation transfer difference NMR reveal a high affinity, which is determined by the methoxy groups at the C-2 and C-3 positions of the quinone headgroup. Using photoactivatable quinone derivatives, it is demonstrated that ubiquinone-8 bound to NqrA occupies a functional site. A novel scheme of electron transfer in Na(+)-NQR is proposed that is initiated by NADH oxidation on subunit NqrF and leads to quinol formation on subunit NqrA.
authors: Department of Neuropathology, University of Freiburg, 79106 Freiburg, Germany.
authors: Marco S
authors: MS
authors: Casutt
authors: Ruslan
authors: R
authors: Nedielkov
authors: Severin
authors: S
authors: Wendelspiess
authors: Sara
authors: S
authors: Vossler
authors: Uwe
authors: U
authors: Gerken
authors: Masatoshi
authors: M
authors: Murai
authors: Hideto
authors: H
authors: Miyoshi
authors: Heiko M
authors: HM
authors: Möller
authors: Julia
authors: J
authors: Steuber
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D042967:Electron Transport Complex I / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014451:Ubiquinone / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D014734:Vibrio cholerae / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D014451:Ubiquinone; C030778:ubiquinone 8; D042967:Electron Transport Complex I; D000254:Sodium-Potassium-Exchanging ATPase