Fig. 1: Block of fast inactivation of rNaV1.5C by LqhIII.
a Left. Normalized current traces from HEK293 cells expressing rNav1.5c in the absence (black) or in the presence of 1 nM (grey), 10 nM (green), 100 nM (blue), or 1000 nM (red) LqhIII. Cells were held at −120 mV and Na+ currents were elicited with a 1000-ms step to 0 mV. Measurements at different toxin concentrations were carried out on different cells because of the limited stability of the whole-cell recording configuration on virus-infected HEK293 cells. Right. Concentration-response curve of LqhIII scorpion toxin for inhibition of fast inactivation of the rNaV1.5C channel. Each point is an average of 4–5 cells. Data-points and error bars represent mean and s.e.m. The solid line represents the Hill equation fit to the data. EC50 = 11.4 ± 0.9 nM (s.e.m., n = 23 cells). b The time course of association of 100 nM of LqhIII scorpion toxin. Cells were held at −120 mV and the toxin was perfused. A pulse to 0 mV from Vm = −120 mV was applied at the indicated times. Single exponential fitting of the block of inhibition ratio showed a time constant of 11.3 min. Each point is an average of six cells. Data points and error bars represent mean and s.e.m. c Time course of LqhIII dissociation. A three-pulse protocol was applied: first, a pulse from −120 mV to +100 mV for the indicated times, followed by a second 50-ms hyperpolarizing pulse to allow recovery from fast inactivation, and finally by the third pulse of 50 ms to 0 mV to measure the extent of recovery of fast inactivation kinetics. Mean and s.e.m.; n = 5 cells for each data point. Inset, representative traces showing recovery of fast inactivation. Source Data are provided as a Source Data File.
