Localization of ubiquinone-8 in the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae.
Casutt, Marco S;
Nedielkov, Ruslan;
Wendelspiess, Severin;
Vossler, Sara;
Gerken, Uwe;
Murai, Masatoshi;
Miyoshi, Hideto;
Möller, Heiko M;
Steuber, Julia;
(2011)
Localization of ubiquinone-8 in the Na+-pumping NADH:quinone oxidoreductase from Vibrio cholerae.
The Journal of biological chemistry, 286 (46).
pp. 40075-40082.
ISSN 1083-351X
DOI: https://doi.org/10.1074/jbc.M111.224980
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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.