Erythrocyte Membrane Polyphosphoinositide Metabolism and the Regulation of Calcium Binding

摘要: Abstract The terminal phosphate of ATP is incorporated into erythrocyte membrane polyphosphoinositides at the rate 1.5 nmoles per min mg protein in presence 10 mm Mg2+ and 0.5 ATP. amount polyphosphoinositide monophosphate can be doubled 30 min. Phosphorylation proceeds until entire supply phosphatidylinositol exhausted. Inhibition incorporation by Ca2+ depends on concentration medium. Incorporation also lower detergent, although it may restored to normal addition exogenous phosphatidylinositol. An Arrhenius plot reaction had two linear portions with a transition 17°. As increased, calcium bound elevated. lowest detectable binding site (Kassoc 4 x 104 liters mole) appears affected. Calcium this increases 1:1 molar ratio increased monophosphate. too low account for increase binding. Membranes elevated levels have much higher Ca2+-ATPase activity than membranes levels, (Na+ + K+)-ATPase not increased. data provide first direct evidence that inositides involved regulation intracellular levels.