Figure 5. V_m-dependent gating of ClC-2 at different [H⁺]_o and [Cl⁻]_i ions.

A, B, C and D, families of G_norm(V_m) curves at different [H⁺]_o from cells dialysed with 40 (A, 5 < n < 9), 80 (B, 4 < n < 10), 140 (C, 4 < n < 11) and 200 (D, 4 < n < 8) mm Cl⁻. [H⁺]_o were: 10^−9.1 (▾), 10^−8.4 (▴), 10^−7.3 (•;), and 10^−6.4 m (▪). The [H⁺]_i = 10^−7.3 m and [Cl⁻]_o = 140 mm was the same in all cases. Note that G_norm was >0 when the [H⁺]_o was 10^−9.1 m in all cases. Continuous lines are fits with eqn (6) (from Scheme II) used to calculate pK_O and β_o/α₀ ratio. The resulting parameters were: [Cl⁻]_i = 40 mm: B = 2.95, A = 1492, z = −1.02, pK_O = 7.8, z_h = −0.017; [Cl⁻]_i = 80 mm: B = 5.59, A = 350, z = −0.89, pK_O = 7.9, z_h = −0.016; [Cl⁻]_i = 140 mm: B = 3.2, A = 255, z = −0.83, pK_O = 7.96, z_h = 0; [Cl⁻]_i = 200 mm: B = 3.1, A = 68.8, z = −0.71, pK_O = 8.0, z_h = 0.008. SEM were similar for all V_m and for clarity only high and low [H⁺]_o are included. E, pK_O vs. V_m at different [Cl⁻]_i. F, β₀/α₀ ratio vs. V_m curves for C↔O transition (Scheme II) at different [Cl⁻]_i. Continuous lines are fits using eqn (7) with z = −0.79, −0.75, −0.75 and −1.13 for 40, 80, 140 and 200 mm Cl⁻, respectively. G, τ_C vs.[H⁺]_o at different [Cl⁻]_i. Continuous lines are fits with eqn (9). For E, F and G curves [Cl⁻]_i was (in mm): (□ = 40; ○ = 80; ▵ = 140, and ▿ = 200 mm). Triangles and inverted triangles plotted at +60 mV in panel E are pK_o values obtained from fitting eqn (9) to data shown in panel G.