Figure 4.

Efflux of ⁶⁰Co²⁺ in the presence of Tc or of ²²Na⁺ from preloaded TetA(L)–H₆ proteoliposomes upon imposition of either an inwardly directed proton gradient or a diffusion potential, outside positive. Proteoliposomes were loaded with 100 mM potassium acetate and either 100 μM ⁶⁰Co²⁺ plus 50 μM nonradioactive Tc (A) or 1 mM ²²Na⁺ (B). During the loading, 2.5 μM valinomycin was also present in all but the control sample with no valinomycin (□). The experiment was initiated by the dilution of the appropriately loaded proteoliposomes into buffers at pH 7.0 and containing 5 μM valinomycin and 100 mM potassium acetate (▪), potassium gluconate (▴), or choline acetate (•). The control with no valinomycin was diluted into buffer lacking valinomycin and containing 100 mM potassium acetate.