Fig. 4.

ATP-dependent H⁺ transport. Washed membrane vesicles (final concentration 0.32 mg/mL) were incubated in 1 mL of 5 mM Pipes, 5 mM Tricine, 25 mM MgSO₄, 150 mM KCl, and 4 μM ACMA. (A) Effect of DCCD on H⁺ transport at pH 7. ATP (2 mM) was added as indicated (black arrow). The quenching was abolished by 20 μL saturated (NH₄)₂SO₄ (gray arrow). The reaction was inhibited by DCCD (750 μM) (gray line). The Na⁺ concentration in the assay was 1 mM. (B) Effect of NaCl and pH on H⁺ transport. The pH and NaCl concentration were as indicated. The quenching percentage is plotted as a function of assay conditions.