Highly purified gastric membranes were extracted by ionic or non-ionic detergents. Further fractionation was carried out on acrylamide gel electrophoresis. Some defined bands, incorporated into artificial bilayer membranes, produced discrete conductance changes characteristics of channel activity. A low molecular weight peak, purified through two cycles of electrophoresis was characterized as an anion-selective, positively voltage dependent channel, and a model to account for the action of the transport ATPase incoporating this channel concept is suggested. © 1974.