Endogenous calmodulin and Ca2+-ATPase activity of human erythrocyte membranes

Treatment of calmodulin-depleted erythrocyte membranes with oleic acid solubilizes only a minor fraction of membrane proteins which, however, contains more than 90% of the total endogenous calmodulin. Concomitantly, Ca2+-ATPase is completely and irreversibly inactivated. By treatment with oleic acid in the presence of Ca.ATP the inactivation of Ca2+-ATPase is abolished to a great extent, the loss of endogenous calmodulin, however, is not affected. Thus, a major participation of endogenous calmodulin in the regulation of Ca2+-ATPase of erythrocyte membranes seems to be improbable.