Planar bilayer reconstitution of calcium channels: lipid effects on single-channel kinetics

Sodium current in the absence of divalents was measured through single calcium channels of skeletal muscle transverse tubules incorporated into planar bilayers composed of the negatively charged lipid phosphatidylserine (PS) and neutral lipid phosphatidylethanolamine (PE). Channel kinetics in PE and PS are characterized by the simultaneous presence of openings of long duration (greater than 200 msec) and openings of brief duration (less than 20 msec) grouped into bursts. Accordingly, exponential distributions of open-channel lifetimes could be fitted with at least two time constants. An increase in bilayer mole fraction of PS, from XPS = 0 (pure PE) to XPS = 1.0 (pure PS), decreased open-channel lifetimes by approximately twofold to threefold. Calculations using the Gouy-Chapman theory indicate that channel lifetimes do not correlate with bilayer surface potentials generated by PS.