Lipid structure affects the activity of integral membrane proteins: PMCA as a model

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

Villa Carlos Paz, Córdoba

Congreso; XLII. Reunión Anual de la Sociedad Argentina de Biofísica; 2013

SAB

Integral membrane proteins have central roles in a vast number of vital cellular processes. The enzymic activity of these proteins is affected by the structures of the lipid molecules that surround them in the membrane. The effects of lipid structure on a membrane protein are likely to be complex and unique for each membrane protein. As a model, we chose the plasma membrane calcium pump (PMCA), an integral membrane protein that regulates the intracellular calcium level. In the present work, purified PMCA was reconstituted into different phospholipid-detergent mixed micelles to relate Ca2+-ATPase activity with the lipid environment. We found that: ATPase activity depends on the carbon chain length and on the molar fraction (XPL) of the phospholipid in the mixed micelle. From XPL= 0.4, there is a drop in ATPase activity for the majority of the assayed phospholipids, except for 1,2-Dilauroyl-sn-glycero-3-phosphocholine (DLPC). To understand this behavior, we studied the biophysical properties of those reconstitution systems and found that there was a micelle-vesicle transition starting from XPL=0.3 (followed by Fluorescence Correlation Spectroscopy and Static Light Scattering) for most of the phospholipids. DLPC was also the exception and the transition was found at higher XPL. These results provide insights to develop a model that links the biophysical properties of the system with the enzymatic activity. With grants of CONICET, FONCyT and UBA.