Extended Data Figure 6. Biophysical characterization of verapamil block of Ca_VAb and functional properties of Ca_VAb T206S.

a, Chemical structure of verapamil. b, Concentration dependence of verapamil inhibition of Ca_VAb. The amplitude of the peak Ba2⁺ current was recorded after applying 20 pulses at a frequency of 1 Hz, where the block reaches steady state. The data were fit by a Hill equation assuming a 1:1 binding ratio. n = 4–7 cells. IC₅₀ = 475 ± 25 nM. c, Ba²⁺ currents of Ca_VAb T206S. d, G–V curves. Ca_VAb (black): V_1/2 = 18.8 ± 0.3 mV, k = 3.7 ± 0.43 ( n = 5); Ca_VAb T206S (blue): V_1/2 = −15 ±1.8 mV, k = 6.6 ±0.4 ( n =5). e, Current traces of Ca_VAb (black) and Ca_VAb T206S (blue) during a 1-s depolarizing pulse from a holding potential of –120 mV to −10 mV. f, State-dependent inhibition of Ca_VAb T206S by Br-verapamil at 10 μM (black), 25 μM (green), 50 μM (red), and 100 μM (blue). For each curve, n = 4–5 cells.