β1 has little effect on the apparent Ca²⁺ sensitivity of BK in the neutral POPE/POPC bilayer, but dramatically increases the apparent Ca²⁺ in negatively charged lipid bilayers of POPE/POPA, POPE/POPS, and POPE/POPG.

A, Sample currents from a single channel of hSlo α and hSlo αβ1 recorded in POPE/POPC bilayer at low [Ca²⁺] of 6.2 µM with holding potentials from −40 mV to +40 mV. B, Sample currents of a single channel of hSlo α and hSlo αβ1 recorded in POPE/POPC bilayer at high [Ca²⁺] of 22.5 µM with varied holding potentials from −40 mV to +40 mV. C, plots of log Po vs V of BK α (open symbols) and BK αβ1 (filled symbols) recorded at three different [Ca²⁺] concentrations of 6.2 µM (triangles), 15.6 µM (squares) and 22.5 µM (circles) in POPE/POPC bilayers. These data demonstrate that β1 has little effect on the apparent Ca²⁺ sensitivity of the BK channel in POPE/POPC bilayers. D, Plots of log Po – V of BK α (open symbols) and BK αβ1 (closed symbols) in bilayers of POPE/POPC, POPE/POPG, POPE/POPS and POPE/POPA at [Ca²⁺] = 15.6 µM. Error bars represent SEM, n = 3–7.