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Biochim Biophys Acta. 2006 Dec;1757(12):1575-81. Epub 2006 Oct 7.

The proton pumping stoichiometry of purified mitochondrial complex I reconstituted into proteoliposomes.

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Universität Frankfurt, Fachbereich Medizin, Zentrum der Biologischen Chemie, Molekulare Bioenergetik, Theodor-Stern-Kai 7, Haus 26, D-60590 Frankfurt am Main, Germany.


NADH:ubiquinone oxidoreductase (complex I) is the largest and most complicated enzyme of aerobic electron transfer. The mechanism how it uses redox energy to pump protons across the bioenergetic membrane is still not understood. Here we determined the pumping stoichiometry of mitochondrial complex I from the strictly aerobic yeast Yarrowia lipolytica. With intact mitochondria, the measured value of 3.8H(+)/2e indicated that four protons are pumped per NADH oxidized. For purified complex I reconstituted into proteoliposomes we measured a very similar pumping stoichiometry of 3.6H(+)/2e . This is the first demonstration that the proton pump of complex I stayed fully functional after purification of the enzyme.

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