Figure 2. Effects on V₅₀ of endogenously formed S0-S4 disulfide bonds, their reduction, and their QPD-induced reformation at the cell surface.

(A, B) Macroscopic currents (insets) and normalized G-V curves of untreated cells expressing W22C/W203C (A) or W22C/G205C (B), after treatment with 10 mM DTT (pH 7.5) for 5 min, and after subsequent treatment with 40 μM QPD (pH 7.5) for 2 min. Recordings were from outside-out macropatches with 10 μM Ca²⁺ inside the pipette. At each potential, the mean relative conductance averaged from several cells is plotted. The mean G-V curve for pWT1 α is shown as a dashed-line. (C) Mean V₅₀ ± SD of the V₅₀s from the individual fits of the Boltzmann equation to the currents from each cell. The V₅₀s were determined after endogenous disulfide crosslinking (black bars), after subsequent DTT (red bars), and finally after 40 μM QPD (green bars). The mean V₅₀ for pWT1 α is shown as a dashed-line. In C, the macropatches were held at −100 mV (closed state) during the QPD-induced reoxidation. N = 3–11. (D) As C, except that the patches were held at +80 mV (open state) during the application of QPD. The mean V₅₀ for pWT1 α is shown as a dashed-line. * P<0.05, **P<0.01, *** P<0.001, **** P< 0.0001 by one-way Anova followed by Tukey’s post-hoc analysis for multiple comparisons between brackets. Without brackets, comparison to pWT1 αby one-way Anova followed by Tukey’s post-hoc analysis.