A thermodynamic analysis of the interaction of P-ATPases with lipids

F. LUIS GONZÁLEZ-FLECHA

Montevideo, Uruguay

Simposio; 6th International Conference on Biological Physics, 5th Southern Cone Biophysics Congress; 2007

Sociedad Argentina de Biofísica

<!-- @page { size: 21.59cm 27.94cm; margin: 2cm } TD P { margin-bottom: 0cm } P { margin-bottom: 0.21cm } --> Integral membrane proteins are polypeptide chains that span biological membranes defining a lipid-protein interface. From early EPR and NMR studies it is well-known that lipids in a first layer surrounding integral membrane proteins have different dynamic properties than the bulk lipids. The number of these perturbed lipids -called boundary lipids- identified by different methods shows a good correlation with the calculated area of the hydrophobic transmembrane surface of membrane proteins. Additionally, fluorescence spectroscopy, chemical cross-linking and, more recently, the analysis of membrane protein crystals provides evidence for preferential interactions between particular lipid species and proteins. On the other hand, several  experimental studies have revealed the importance of bound lipids for the stability and function of membrane proteins. Despite their central role in membrane protein assembly and function, the thermodynamics of lipid/protein interactions is poorly understood. In this work we present a simple adsoprtion equilibrium model describing the interactions among amphiphiles on the hydrophobic transmembrane surface of membrane proteins. A thermodynamic analysis based on this model is used to obtain the thermodynamic parameters for the exchange process. This formalisms is applied to the  thermodynamic characterization of the interactions between P-type ATPases and different lipids. Differences in phospholipid affinity support the idea that these proteins select a specific microenvironment when they are inserted in a multicomponent micellar phase. With grants from UBA, CONICET and ANPCyT