Transmembrane domain dimerization induces cholesterol rafts in curved lipid bilayers

Are the dimerization of transmembrane (TM) domains and the reorganization of the lipid bilayer two independent events? Does one event induce or interfere with the other? In this work, we have performed well-tempered metadynamics simulations to calculate the free energy cost to bend a model ternary lipid bilayer in the presence of a TM peptide in its dimer form. We have compared this result with the free energy cost needed to bend a bilayer-only system. Additionally, we have calculated the free energy cost to form a model TM peptide dimer quantitatively describing how lipids reorganize themselves in response to the increase of the membrane curvature and to the lipid-peptide interactions. Our results indicate that the formation of the peptide dimer inside the bilayer increases the cost of the membrane bending due to the spontaneous clustering of cholesterol molecules.