Modulation of Plasma Membrane Ca2+-ATPase by neutral phospholipids: Effect of the micelle ? vesicle transition and the bilayer

MARIA FLORENCIA PIGNATARO; MARTÍN DODES-TRAIAN; LUIS GONZALEZ-FLECHA; MAURICIO SICA; IRENE CECILIA MANGIALAVORI; JUAN PABLO F.C. ROSSI

Sierra de la Ventana

Congreso; XLIII. Reunión Anual de la Sociedad Argentina de Biofísica; 2014

The effects of lipid structure on a membrane protein are likely to be complex and unique for each membrane protein. Here we employed different detergent-phosphatidylcholine reconstitution media and study their effects on PMCA. We found that Ca2+-ATPase activity largely depends on the length and the unsaturation degree of the hydrocarbon chain. The biophysical properties of the detergent-phosphatidylcholine mixtures lead to a biphasic behavior of PMCA activity regardless the length of the hydrocarbon chain. Using Fluorescence Correlation Spectroscopy, we monitored the micelle-vesicle transition in this system and found that the transition ensues at XPC= 0.3 for DMPC and at 0.6 for DLPC. We found a decrease in PMCA turnover after the micelle-vesicle transition, but the time of residence of the phosphorylated intermediate (EP) increase with the concentration of XPC. Maximal PMCA activity is obtained in detergent/DMPC micelles in agreement with functional and structural analysis of the hydrophobic domain thickness. Results in this paper show that at optimal protein/phospholipid stoichiometry, ATPase activity is higher when the hydrophobic thickness of the lipid bilayer is expected to match the transmembrane domain of the protein, reducing the thermodynamic cost of exposing either fatty acyl chains or hydrophobic amino acids to water. With grants from UBACYT, ANPCYT y CONICET