Gibbs energy determinants of lipoprotein insertion into lipid membranes: the case study of Ras proteins.

In a combined chemical-biological and biophysical approach we explored the Gibbs (free) energy contributions to the membrane partitioning of lipidated proteins, and compared the theoretical predictions with recent experimental data on the membrane insertion of Ras proteins of various anchor systems into rationally designed model biomembrane systems. Various factors fostering or reducing the membrane partitioning properties are discussed, including hydrophobic effects, lipid chain mismatch, electrostatic interactions, membrane-mediated protein-protein interactions, and terms that account for line tension effects between coexisting lipid domains, lipid sorting, and changes in the lateral organization of the lipid bilayer system. From these data, it is apparent that two membrane anchoring motifs are needed to facilitate firm membrane binding. For heterogeneous membranes, localization and sequestration at domain boundaries as well as formation of protein clusters and collective lateral organization via an effective lipid sorting mechanism provide complementary ways of inducing membrane nanodomains that could potentially operate as effective, high fidelity signalling platforms.