Figure 5

Chloride transport in valinomycin-“shunted” membranes. Chloride efflux induced by the anionophore 1b (4 µM) recorded in LUVs with 450 mM KNO₃ and 20 mM HEPES, pH 7.0 in the external solution (a and b), and with 300 mM K₂SO₄ and 20 mM HEPES, pH 7.0 in the external solution (c and d). The LUV contained 450 mM KCl and 20 mM HEPES, pH 7.0. (a) Addition of valinomycin (1 µg/ml) does not induce any chloride efflux, and successive application of the anionophore induced a consistent chloride efflux. (b) When valinomycin is added after 1b induced chloride efflux is initiated, it does not modify the time course of the transport. (c) In the presence of the external impermeable anion, a robust chloride efflux is observed when the anionophore 1b is applied in presence of valinomycin. (d) The anionophore elicits a very small chloride efflux when the external anion is impermeable, but it significantly increases upon the application of valinomycin.