Figure 4.

Ca²⁺ increases MthK open probability by increasing burst frequency. (A) Mean closed and open dwell times within a burst in 0 and 5 mM Ca²⁺. (B) Mean gap duration and burst duration in 0 and 5 mM Ca²⁺. Bars are mean ± SEM from at least three separate bilayers (open, 0 Ca²⁺) and 10 bilayers (solid, 5 mM Ca²⁺). (C) Closed dwell time histograms for a single bilayer containing two channels. The bilayer was perfused from 5 mM Ca²⁺ to 0 Ca²⁺. The fits are with Eq. 4 with two exponential components with: A₁ = 0.97 ± 0.09, τ₁ = 0.23 ± 0.12, A₂ = 0.03 ± 0.06, and τ₂ = 118 ± 3 for 5 mM Ca²⁺, and A₁ = 0.88 ± 0.05, τ₁ = 0.30 ± 0.08, A₂ = 0.12 ± 0.04, and τ₂ = 22552 for 0 Ca²⁺. Inset shows magnification of histogram data for closures ≥10 ms; smooth line is the exponential fit.