Regulation of plasma membrane Ca2+ ATPases by lipids of the phosphatidylinositol cycle.

When the erythrocyte plasma membrane Ca2+ pump is reconstituted into phosphatidylcholine liposomes, the inclusion of small amounts of phosphatidic acid or phosphatidylinositol 4,5-bisphosphate stimulates the enzyme's activity. Other lipids of the phosphatidylinositol cycle (diacylglycerol, phosphatidylinositol) have little effect. The stimulatory effect of phosphatidylinositol 4,5-bisphosphate is greater than that of calmodulin; this lipid also stimulates the plasma membrane Ca2+ ATPase from rat brain.