Fig. 2: 1PBC block is state-dependent.

a Concentration-response relations of 1PBC at the indicated intracellular Ca²⁺ concentrations at 80 mV. Data are scaled according to the open probability of the channel in the absence of 1PBC as determined previously²⁸. Data are averages of 6, 5, and 7 biological replicates for 2 µM, 800 nM, and 400 nM Ca²⁺ respectively, errors are SEM. b IC₅₀ values at the plotted intracellular Ca²⁺ concentrations at 80 mV, which were obtained via an empirical fit to the Hill equation on the data shown in (a). Shown are the best-fit values, errors are 95% CI. a, b Solid lines are a global fit to an open-channel block mechanism (Eqs. 4–9), with estimated parameters K_{d 1PBC} = 3.6 ± 0.29 µM at zero mV and apparent valence δ_b = 0.27 ± 0.025 (see “Methods”). c Concentration-response relations of 1PBC at 0 mV at zero and 2 µM intracellular Ca²⁺ for the constitutively active mutants I551A and Q649A. Data are averages of 6, 9, 7, and 7 biological replicates for I551A at 2 µM Ca²⁺, I551A at 0 Ca²⁺, Q649A at 2 µM Ca²⁺, and Q649A at 0 Ca²⁺ respectively, errors are SEM. Solid lines are fits to the Hill equation. Dashed lines are the relation of WT.