FIG. 2.

Influence of pH on NADH-driven Na⁺ transport by NDH-1. NADH-driven Na⁺ uptake (•) by NDH-1 purified by anionic-exchange chromatography in the buffer used for the reconstitution of the complex into proteoliposomes (10 mM HEPES-KOH, 50 mM KCl, 10% glycerol) was monitored. The protein-to-lipid ratio was 1:4. At time zero, 0.1 mM NADH and 5 mM NaCl were added, and the Na⁺ content of the proteoliposomes was determined at the indicated times. In the control reactions, NADH was omitted (▪). (A) Proteoliposomes containing NDH-1. Na⁺ transport at pH 6.5 or pH 7.5 was monitored. (B) Proteoliposomes containing NDH-1 and the H⁺-translocating ATPase. Na⁺ transport at pH 7.0 was monitored.