EFFECTS OF PHOSPHOLIPIDS ON BINDING OF CALCIUM TO (CA-2+-MG-2+)-ATPASE

The (Ca2+–Mg2+)-ATPase purified from skeletal muscle sarcoplasmic reticulum binds two Ca2+ ions per ATPase molecule. On reconstitution into bilayers of dioleoylphosphatidylcholine ((C18:1)PC) or dinervonylphosphatidylcholine ((C24:1)PC) the stoichiometry of binding remains unchanged, but when the ATPase is reconstituted into bilayers of dimyristoleoylphosphatidylcholine ((C14:1)PC) the stoichiometry changes to one Ca2+ ion per ATPase molecule. Nevertheless, the level of phosphorylation is the same for the ATPase reconstituted with (C18:1)PC or (C14:1)PC. The effect of (C14:1)PC on the stoichiometry of Ca2+ binding is prevented by androstenol at a 1:1 molar ratio with the phospholipid. © 1990, American Chemical Society. All rights reserved.