| Abstract: | Three plasma membrane subfractions have been isolated and characterized from rat liver cells. The high affinity Ca2+-stimulated ATPase is highly enriched in the bile canalicular subfraction. Taking into account cross-contamination by the blood sinusoidal and lateral membranes it is suggested that the high-affinity Ca2+-ATPase is located exclusively in this fraction. The high-affinity Ca2+-ATPase is coupled to Ca2+ transport, is calmodulin-insensitive, sensitive to vanadate under appropriate experimental conditions and is strongly inhibited by La3+. In the presence of Ca2+ and ATP the ATPase forms a phosphorylated intermediate of molecular mass about 200 kDa. |
