Phase-Transition-Induced protein redistribution in Lipid Bilayers

We report an atomic force microscopy study on the lateral spatial redistribution of an integral membraneprotein reconstituted in supported lipid bilayers (SLBs) subjected to a thermally induced phase transition.KcsA proteins were reconstituted in proteoliposomes of POPE/POPG (3:1, mol/mol), and SLBs, includingthe proteins, were then obtained by the vesicle fusion technique on mica. By decreasing the temperature, thelipid bilayer passed from a liquid disordered (ld) phase in which the proteins are homogeneously distributedto a coexistence of solid ordered (so) and ld domains with the proteins preferentially distributed in the lddomains. The inhomogeneous distribution eventually led to protein clustering. The obtained results are discussedin light of the role that the lipid/protein interaction can have in determining the function of integral membraneproteins.