Modulation of Plasma Membrane Ca2+-ATPase by Neutral Phospholipids: Effect of the Micelle-Vesicle Transition and the Bilayer Thickness

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

JOURNAL OF BIOLOGICAL CHEMISTRY

AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC

Lugar: Bethesda, Maryland; Año: 2015

0021-9258

Modulation of Plasma Membrane Ca2+-ATPase by Neutral Phospholipids: Effect of the Micelle-Vesicle Transition and the Bilayer Thickness María Florencia Pignataro1, Martín M. Dodes-Traian1, F. Luis González-Flecha1, Mauricio Sica2, Irene C. Mangialavori1# and Juan Pablo F. C. Rossi1 1Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956 (1113) Buenos Aires, and 2Laboratorio de Bioenergías, IEDS, CONICET Centro Atómico Bariloche, E. Bustillo 9,500(8400) San Carlos de Bariloche, Río Negro, Argentina Running title: Neutral Phospholipids modulate PMCA activity #To whom correspondence should be addressed: Irene Mangialavori, Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956 (1113) Buenos Aires, Argentina. Mail: irenem@qb.ffyb.uba.ar Keywords: Ca2+-ATPase, micelles, vesicles, hydrophobic thickness, functional model The effects of lipids on membrane proteins are likely to be complex and unique for each membrane protein. Here we studied different detergent/phosphatidylcholine reconstitution media and tested their effects on Plasma Membrane Ca2+-pump (PMCA). We found that Ca2+-ATPase activity has a biphasic behaviour respect to the detergent/phosphatidylcholine ratio, whose maximal value largely depends on the length and the unsaturation degree of the hydrocarbon chain. Using Static Light Scattering and Fluorescence Correlation Spectroscopy, we monitored the changes in hydrodynamic radius of detergent/phosphatidylcholine particles during the micelle-vesicle transition. We found that, when PMCA is reconstituted in mixed micelles, neutral phospholipids increase the enzyme turnover. The biophysical changes associated to the transition from mixed micelles to bicelles, increase the time of residence of the phosphorylated intermediate (EP) decreasing the enzyme turnover. Molecular Dynamics simulations analysis of the interactions between PMCA and the phospholipid bilayer in which it is embedded show that in the 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) bilayer, charged residues of the protein are trapped in the hydrophobic core. Conversely, in the 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayer, the overall hydrophobic?hydrophilic requirements of the protein surface are fulfilled the best, reducing the thermodynamic cost of exposing charged residues to the hydrophobic core. The apparent mismatch produced by a DOPC thicker bilayer, could be a structural foundation to explain its functional implication on PMCA.