title: Modulation of plasma membrane Ca2+-ATPase by neutral phospholipids: effect of the micelle-vesicle transition and the bilayer thickness.
abstract: 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 Ca(2+) pump (PMCA). We found that Ca(2+)-ATPase activity shows a biphasic behavior with respect to the detergent/phosphatidylcholine ratio. Moreover, the maximal Ca(2+)-ATPase activity 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 with 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 bilayer, charged residues of the protein are trapped in the hydrophobic core. Conversely, in the 1,2-dimyristoyl-sn-glycero-3-phosphocholine 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 1,2-dioleoyl-sn-glycero-3-phosphocholine thicker bilayer could be a structural foundation to explain its functional effect on PMCA.
authors.affiliation: From the Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956 (1113) Buenos Aires, Argentina and.
authors.forename: María Florencia
authors.initials: MF
authors.lastname: Pignataro
authors.affiliation: From the Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956 (1113) Buenos Aires, Argentina and.
authors.forename: Martín M
authors.initials: MM
authors.lastname: Dodes-Traian
authors.affiliation: From the Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956 (1113) Buenos Aires, Argentina and.
authors.forename: F Luis
authors.initials: FL
authors.lastname: González-Flecha
authors.affiliation: the Laboratorio de Bioenergías, IEDS, CONICET Centro Atómico Bariloche, E. Bustillo 9,500 (8400), San Carlos de Bariloche, Río Negro, Argentina.
authors.forename: Mauricio
authors.initials: M
authors.lastname: Sica
authors.affiliation: From the Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956 (1113) Buenos Aires, Argentina and irenem@qb.ffyb.uba.ar.
authors.forename: Irene C
authors.initials: IC
authors.lastname: Mangialavori
authors.affiliation: From the Instituto de Química y Fisicoquímica Biológicas, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, CONICET, Junín 956 (1113) Buenos Aires, Argentina and.
authors.forename: Juan Pablo F C
authors.initials: JP
authors.lastname: Rossi
mesh_terms: D002462:Cell Membrane / Q000201:enzymology*; D018360:Crystallography, X-Ray; D003902:Detergents / Q000737:chemistry / Q000378:metabolism; D004912:Erythrocytes / Q000737:chemistry; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008051:Lipid Bilayers / Q000737:chemistry* / Q000378:metabolism; D008823:Micelles; D056004:Molecular Dynamics Simulation; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation
chemical_list: D003902:Detergents; D008051:Lipid Bilayers; D008823:Micelles; D010713:Phosphatidylcholines; D010743:Phospholipids; D053499:Plasma Membrane Calcium-Transporting ATPases
keywords: Calcium ATPase; Enzyme Turnover; Lipid Bilayer; Molecular Dynamics; Protein Structure