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. 2013 Jan 8;288(8):5487–5495. doi: 10.1074/jbc.M112.441964

FIGURE 3.

FIGURE 3.

State-dependent reactivity of Cys at positions 79 and 416. A, reactivity toward MTSET of E79C and E416C channels in the closed and desensitized states. Shown are representative recordings of experiments performed with oocytes expressing E79C and E416C channels. Whole-cell currents were elicited by a change in extracellular pH from 8.0 to 5.0 before and after exposure to MTSET (1 mm) at the indicate pH values. Untreated oocytes expressing E79C and E416C channels served as controls. B and C, proton activation curves for E79C and E416C channels before (white circles) and after (gray circles) MTSET modification. E79C and E416C channels were covalently modified by MTSET (1 mm) at pH 8.0. Proton-activated currents were elicited by a drop in extracellular pH from 9.0 to solutions of lower pH. Currents were normalized to the signal obtained at pH 4.0 (n = 8–18). D, chemical modification of E79C and E416C channels in the closed and desensitized states. Whole-cell currents were evoked by a change in extracellular pH from 8.0 to 5.0 as described for A. The relative response represents the ratio of the pH-elicited peak current following MTSET (ET) treatment (or control) to the pH-elicited peak current before treatment (n = 10–24). Statistically significant differences are indicated: **, p < 0.01; +, p < 0.001 (Kruskal-Wallis test followed by Dunn's multiple comparison test). E, state-dependent modification of E79C channels. Shown is the fractional activation as a function of the preconditioning pH (left axis, black circles). Whole-cell currents were elicited by extracellular acidification to pH 5.0 from a solution of pH 9.0, 8.0, 7.6, 7.4, 7.2, or 7.0. Currents were normalized to the peak current evoked by a drop in extracellular pH from 9.0 to 5.0 (n = 9–10). Shown is the chemical modification of E79C as a function of the pH of MTSET treatment (right axis, gray circles). Whole-cell currents were elicited by a change in extracellular pH from 8.0 to 5.0 before and after exposure to MTSET (1 mm) at pH 7.0, 7.2, 7.4, 7.6, or 8.0. The relative response represents the ratio of the pH-elicited peak current following MTSET treatment to the pH-elicited peak current before treatment (n = 8–24). Data were normalized to the mean relative response to extracellular acidification of E79C channels exposed to MTSET at pH 8.0.