Dose–response curves of various wild-type and mutant TMEM16A channels. (A) Comparison of the dose–response curves of WT∙WT, E698C∙E698C, E698C-E698C, and E698C-WT obtained at −40 mV (top) and 40 mV (bottom). The dose–response curve of the WT∙WT channel was obtained from Ni et al. (2014). Values of K_1/2 (µM) and h for WT∙WT, E698C∙E698C, and E698C-E698C are shown. The curves for the tandem heterodimeric channel (E698C-WT) in two regions were scaled from the dose–response curves of the WT∙WT channel (I = a × I_WT∙WT, black) and the E698C∙E698C channel (I = a + (1 − a) × I_{E698C∙E698C}, red), where the values of a (0.39 and 0.44 in the top and bottom panel, respectively) were determined by averaging the values of I_norm at [Ca²⁺] = 3.13 µM and [Ca²⁺] = 5 µM. (B) Comparison of the dose–response curves of WT∙WT, E701C∙E701C, and E701C-WT obtained at −40 mV (top) and 40 mV (bottom). Values of the K_1/2 and h for E701C∙E701C are not depicted because of the lack of current saturation in the dose–response curve. The curves for E701C-WT were scaled from those of the WT∙WT channel (I = b × I_WT∙WT, black) and the E701C∙E701C channel (I = b + (1 − b) × I_{E701C∙E701C}, red). The values of b (0.542 and 0.566 in the top and bottom panel, respectively) were obtained by averaging the values of I_norm at [Ca²⁺] = 3.13 µM and [Ca²⁺] = 5 µM. All data points in A and B are depicted as mean ± SEM. The fitted values of K_1/2 and Hill coefficient are shown next to the fitted curves.