Fig. 2

The channel currents of mutant SLO-2 (H159Y) are larger than those of wild type. a Representative whole-cell current recordings of HEK293T cells expressing either wild-type (n = 3, 6, 6, 8, 4, 4) or H159Y mutant (n = 4, 5, 5, 6, 6, 4) SLO-2 channels by patch clamp method are shown. Cells were held at −60 mV and depolarizing step pulses (200 ms) were applied as indicated above the current traces. Intracellular Ca²⁺ concentration ([Ca²⁺]_i) is indicated above the current traces. b Current densities were measured at the end of step pulses and averaged for each membrane potential and [Ca²⁺]_i and are plotted against membrane potential. Currents were recorded in distinct cells, and the numbers of replications for wild-type and H159Y channels are indicated. The error bars represent the SEM. c Conductance (G) was measured as the tail current amplitude at 0 mV after various step-pulse stimulations and was normalized to the recorded maximal amplitude at the most depolarized potential (G_max). Normalized conductance (G/G_max) is plotted against membrane potential. The meaning of the symbols is indicated in the figure. The error bars represent the SEM. d The voltage at half-maximal activation(V_1/2) of wild-type and H159Y mutant channels calculated from c is plotted against [Ca²⁺]_i. Horizontal bars represent medians. *p < 0.05, **p < 0.01, ***p < 0.001 (Welch two-sample t test). e Current density at depolarization of a 50 mV pulse was measured and averaged for each [Ca²⁺]_i and then plotted against [Ca²⁺]_i. Horizontal bars represent medians. f The activation time constants were obtained by fitting the outward current traces to double exponential functions. The fast time constants are plotted against membrane potential. Horizontal bars represent medians. g The fraction of instantaneously opening channels was calculated as the fraction of constant components of the fitting curves and is plotted against the membrane potential. Horizontal bars represent medians