Laboratoire de Physique Théorique
Toulouse - UMR 5152

We propose a realistic scenario accounting for the existence of sub-micrometric protein domains in cell membranes. At the biological level, such membrane domains have been demonstrated to be specialized, in that sense that they congregate one or a few protein species amongst the hundreds of different species that a cell membrane may contain, in order to perform a determined biological task. By analyzing the balance between mixing entropy and protein affinities, we elucidate by statistical mechanics arguments how such protein sorting in distinct domains can be explained without appealing to pre-existing lipidic micro-phase separations, as in the lipid raft scenario. At equilibrium, it is preferable to co-localize certain proteins because the ensuing energetic gain is larger than the concomitant entropic cost. This alternative mechanism is discussed to be compatible with known physical interactions between membrane proteins.