¨Lipid-protein interactions In Plasma Membrane Calcium Pump: A fluorescence and photolabeling study¨

MANGIALAVORI IRENE; VILLAMIL GIRALDO, A. M.; ROSSI, J.P.F.C.

MONTEVIDEO, URUGUAY

Congreso; .34th Annual Meeting of the Argentine Biophysical Society; 2007

SOCIEDAD ARGENTINA DE BIOFISICA

¨Lipid-protein interactions In Plasma Membrane Calcium Pump: A fluorescence and photolabeling  study¨ Irene Mangialavori1, Ana María Villamil Giraldo1, and Juan Pablo F.C. Rossi*1   The purpose of this work was to obtain further structural information about membrane regions of PMCA and their interaction with surrounding lipids, using SERCA as a template. To this end, we have used the photoactivatable phosphatidylcholine analog [125I]TID-PC/16 that had been used previously to analyze lipid–protein interfaces (13–15). With a similar approach, we determined that: (1) The reagent is sensitive to detect conformational changes of calcium pumps induced by the substrate, inhibitors and activators (2) Comparison of PMCA and SERCA show that PMCA fully activated by calmodulin or removing by proteolysis its C-terminal domain resembles to SERCA. (3) In the basal non-activated state PMCA exposes up to 45% more hydrophobic surface than the enzyme in E2 and up to 65% more than the fully activated enzyme. (4) Comparison of the experiments in this work and the crystallographic structure of different conformations of SERCA suggest that increase of TID-PC incorporation is related with increased exposure of transmembrane helices surface to surrounding lipids.