Effects of lipid structure on the function of the Ca2+-ATPase of skeletal muscle of sarcoplasmic reticulum are reviewed. Binding of phospholipids to the ATPase shows little specificity. Phosphatidylcholines with short (C14) or long (C24) fatty acyl chains have marked effects on the activity of the ATPase, including a change in the stoichiometry of Ca binding. Low ATPase activity in gel phase lipid follows from low rate of phosphorylation. Phosphatidylinositol 4-phosphate increases ATPase activity by increasing the rate of dephosphorylation of the phosphorylated ATPase. Stimulation is not seen with other anionic phospholipids; phosphatidic acid decreases ATPase activity in a Mg2+-dependent manner.
Abbreviations di(C14:1)PC, dimyristoleoylphosphatidycholine; di(C16:0)PC, dipalmitoylphosphatidylcholine; di(C18:1)PC, dioleoylphosphatidylcholine; di(Br2C18:0)PC, dibromostearoylphosphatidylcholine; di(C24:1)PC, dinervonylphosphatidylcholine; di(C18:1)PA, dioleoylphosphatidic acid; di(C18:1)PE, dioleoylphosphatidylethanolamine; Ptdlns, phosphatidylinositol; PtdIns-4P, phos-phatidylinositol 4-phosphate;