Ion-gated channel induced in planar bilayers by incorporation of (Na+,K+)-ATPase

Abstract

An ion-gated channel was conferred on a planar lipid bilayer membrane upon incorporation of (Na+,K+)-ATPase. The channel exhibited two conductance states. The high conductance state was only observed when an ion gradient was present across the planar membrane. This state corresponded to an enzyme conformation which was ouabain and vanadate sensitive (i.e. conductance was inhibited by these compounds), while the low conductance state showed no sensitivity to either inhibitor. Single channel conductance behavior was observed when minimal amounts of enzyme were incorporated into the planar bilayer. The observed single channel conductance was 270 +/- 14 picosiemens. Similar transport behavior was observed for enzyme purified from ovine kidney using sodium dodecyl sulfate (anionic), eel electroplax using Lubrol-WX (nonionic), and kidney microsomes. In addition, the data strongly suggest that enzyme from the kidney microsomes was asymmetrically incorporated into the planar bilayer.