期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 286, 期 46, 页码 40075-40082出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M111.224980
关键词
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资金
- Swiss National Science Foundation [PP0033-118994]
- Baden-Wurttemberg Stiftung
- Forschungsprogramm P-LS-Meth/4
- Japan Society for the Promotion of Science [20380068]
- Swiss National Science Foundation (SNF) [PP0033-118994] Funding Source: Swiss National Science Foundation (SNF)
- Grants-in-Aid for Scientific Research [23780116, 20380068] Funding Source: KAKEN
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.
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