NADH oxidation drives respiratory Na+ transport in mitochondria from Yarrowia lipolytica.
It is generally assumed that respiratory complexes exclusively use protons to energize the inner mitochondrial membrane. Here we show that oxidation of NADH by submitochondrial particles (SMPs) from the yeast Yarrowia lipolytica is coupled to protonophore-resistant Na+ uptake, indicating that a redox-driven, primary Na+ pump is operative in the inner mitochondrial membrane. By purification and reconstitution into proteoliposomes, a respiratory NADH dehydrogenase was identified which coupled NADH-dependent reduction of ubiquinone (1.4 micromol min(-1) mg(-1)) to Na+ translocation (2.0 micromol min(-1) mg(-1)). NADH-driven Na+ transport was sensitive towards rotenone, a specific inhibitor of complex I. We conclude that mitochondria from Y. lipolytica contain a NADH-driven Na+ pump and propose that it represents the complex I of the respiratory chain. Our study indicates that energy conversion by mitochondria does not exclusively rely on the proton motive force but may benefit from the electrochemical Na+ gradient established by complex I.
Biochemisches Institut, Universität Zürich, 8057, Zurich, Switzerland.
Po-Chi
PC
Lin
Andrea
A
Puhar
Julia
J
Steuber
D008928:Mitochondria / Q000378:metabolism*; D009243:NAD / Q000378:metabolism*; D010084:Oxidation-Reduction; D011808:Quinone Reductases / Q000302:isolation & purification / Q000378:metabolism; D012402:Rotenone / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D014451:Ubiquinone / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology; D025062:Yarrowia / Q000378:metabolism*
D014475:Uncoupling Agents; D012402:Rotenone; D009243:NAD; D014451:Ubiquinone; D012964:Sodium; C041831:NADH dehydrogenase (quinone); D011808:Quinone Reductases