Fig. 4: Functional characterization of the dual receptor sites for BTX-B. | Nature Communications

Fig. 4: Functional characterization of the dual receptor sites for BTX-B.

From: Dual receptor-sites reveal the structural basis for hyperactivation of sodium channels by poison-dart toxin batrachotoxin

Fig. 4

a Location of F1762 (red stick) in DIV-S6 near Site IIB2 (cyan sticks). b Locations of F399 and F403 (blue sticks) in DI-S6 and F1707, M1768, and Y1769 (red sticks) in DIV P-loop and S6 near Site IIB2 (bright green sticks). c Raw traces of the peak current for rNaV1.5c WT and mutants in the presence of 10 μM BTX-B. Raw traces for the mutants were scaled to the trace for the WT. Inward sodium current is plotted downward as a negative quantity, illustrating the rates and extents of voltage-dependent activation and inactivation. d Plot of inactivation ratios Ri at 40 ms following the peak for WT and mutants in the presence of 10 μM BTX-B. See Methods for details. Data are presented as mean values ± SEM with n = 6 cells for WT. Statistical significance was evaluated with Student’s t test (two tailed test with no adjustment). Asterisks * and *** represent p-values ≤ 0.05 and ≤0.001, respectively; ns not significant. p-values: 0.972 (F399A, n = 6), 0.0000397 (F403A, n = 5), 0.0266 (F1707A, n = 3), 0.0130 (M1768A, n = 5), 0.0000845 (F1707A/M1768A, n = 7), 0.0000344 (F1762A, n = 8), and 0.903 (Y1769A, n = 3).

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