Mutation of Glu_ex relieves the high salt inhibition. (A) Schematic representation of the ³⁶Cl⁻ efflux experiments. (B and C) Time course of ³⁶Cl⁻ efflux from proteoliposomes reconstituted with WT CLC-ec1 at 300 mM Cl⁻ or at 1,000 mM Cl⁻ or with the E148A mutant at 300 mM Cl⁻ or at 1,000 mM Cl⁻. Solid lines represent exponential fits of the time courses with time constants (shown in C) of τ^WT(300 Cl) = 1.15 ± 0.18 min, τ^WT(1,000 Cl) = 3.12 ± 0.32 min, τ^E148A (300 Cl) = 12.3 ± 0.5 min, and τ^E148A(1,000 Cl) = 14.5 ± 1.4 min. Symbols represent the mean from four independent experiments, and the error bars are the SEM.