Conformation of peripherally bound membrane proteins: the influence of the lipid phase state

DECCA, M. B.

Carlos Paz, Cordoba

Simposio; SAB 2013: XLII Reunion Anual Sociedad Argentina de Biofísica; 2013

Sociedad Argentina de Biofísica

The transfer of soluble proteins into the interface between the lipid membrane and the aqueous phase is recognized as a key step for several cellular processes. This translocation represents a major change in the protein environment that can stabilize different protein conformations with possible consequences on its biological activity. Using as a model the peripherally bound protein L-BABP we found that conformation can be modulated by the phase state of the lipid membrane.When L-BABP was bound to lipids in the gel phase, the secondary structure was similar to the native structure in solution, membrane transition to the liquid-crystalline phase produced the partial unfolding of the protein. This was observed with anionic phospholipids with different polar headgroup and different melting transition temperature, and it was sensitive to the ionic strength. We explored changes in surface potential as possible triggers of protein unfolding at the interface. We measured membrane electrokinetic potential at different temperatures and we found a correlation with protein conformation: membrane-bound, native-like protein occurred under conditions in which lipid vesicles have low surface potential and unfolded state was observed in membranes with higher values of surface potential. Therefore, changes in protein conformation coupled to lipid phase transitions can result as a consequence of the modification of electrostatic surface potential during lipid melting. We demonstrate the linkage between lipid organization, protein conformation, strength of binding, and membrane electrostatic surface potential.