title: Phosphoinositide-protein interactions of the plasma-membrane Ca2(+)-transport ATPase as revealed by fluorescence energy transfer.
abstract: Fluorescence energy transfer has been used to study the interaction of various phospholipids with the erythrocyte (Ca2+ + Mg2+)-ATPase. The fluorescence energy transfer between tryptophan residues of the (Ca2+ + Mg2+)-ATPase purified from erythrocytes and pyrene-labelled analogues of phosphatidylcholine (Pyr-PC), phosphatidylinositol (Pyr-PI), phosphatidylinositol 4-phosphate (Pyr-PIP), phosphatidylinositol 4,5-bisphosphate (Pyr-PIP2), phosphatidylglycerol (Pyr-PG) and phosphatidic acid (Pyr-PA) was measured. A positive correlation was found between the number of negative charges on the phospholipids (PIP2 greater than PIP greater than PA greater than PI = PG greater than PC) and the potency of their pyrene-labelled analogues to act as quantum acceptors in fluorescence energy transfer from the tryptophan residues of the (Ca2+ + Mg2+)-ATPase. This is the first time that a physical interaction between PIP/PIP2 and an intrinsic membrane protein has been demonstrated. The dependence of the energy transfer on the number of negative charges of the phospholipids closely resembles the previously demonstrated charge dependence of the enzymatic activity of the (Ca2+ + Mg2+)-ATPase (Missiaen, L., Raeymaekers, L., Wuytack, F., Vrolix, M., Desmet, H. and Casteels, R. (1989) Biochem. J. 263, 687-694). It is concluded that the stimulation of the (Ca2+ + Mg2+)-ATPase activity by negatively charged phospholipids is based on a binding of these lipids to the (Ca2+ + Mg2+)-ATPase and that the negative charges are a major modulatory factor for this interaction.
authors.affiliation: Physiological Laboratory, Catholic University of Leuven, Belgium.
authors.forename: J
authors.initials: J
authors.lastname: Verbist
authors.forename: T W
authors.initials: TW
authors.lastname: Gadella
authors.forename: L
authors.initials: L
authors.lastname: Raeymaekers
authors.forename: F
authors.initials: F
authors.lastname: Wuytack
authors.forename: K W
authors.initials: KW
authors.lastname: Wirtz
authors.forename: R
authors.initials: R
authors.lastname: Casteels
mesh_terms: D000818:Animals; D001693:Biological Transport, Active; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D004735:Energy Transfer; D004910:Erythrocyte Membrane / Q000201:enzymology*; D066298:In Vitro Techniques; D008563:Membrane Lipids / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D013552:Swine
chemical_list: D008563:Membrane Lipids; D010716:Phosphatidylinositols; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases