Figure 9.

Changes in membrane potential across proteoliposome detected with voltage-sensitive probe oxonol VI. (A) Effect of CCCP and the permeant anion NO^-₃ on the membrane potential across the proteoliposome built up in the presence of ATP and Na⁺. 8 mM NaCl was initially present in the reaction mixture containing 0.4 M sucrose, 20 mM Hepes-Tris buffer pH 7.6, 1 mM MgSO₄, 3 μM oxonol VI and proteoliposomes (25 μg protein). The reaction was initiated by adding ATP at 4 mM, NaCl at 100 mM, CCCP at 12 μM or KNO₃ at 100 mM as shown by the arrows. (B) Effect of NaCl concentration on the membrane potential across the proteoliposome. NaCl was initially present in the reaction mixture at the concentration of 8 mM. The reaction was initiated by adding ATP at 4 mM and NaCl at various concentrations as shown by the arrows.