Title: The raft hypothesis: still at sea after all these years, or some possible ways to organize the plasma membrane
Abstract: An extremely fruitful hypothesis has been that the plasma membrane, which surrounds all cells, is not spatially homogeneous, but rather is heterogeneous. It is characterized by agglomerations of cholesterol and saturated lipids which float, like rafts, in a sea of unsaturated lipids. Because the molecules which anchor proteins to the membrane can distinguish between rafts and sea, and prefer one to the other, the picture implies that proteins are not distributed randomly across the membrane but rather will cluster, and therefore perform their functions more efficiently. Thus the appealing idea that physical organization leads to functional organization. The difficulties with this picture are both experimental and theoretical: of the former, almost all of the evidence for the existence of rafts is indirect; of the latter, where does the characteristic size of the raft, on the order of 100 nm, come from? Why should molecules agglomerate in the first place? I shall introduce the players in this drama, provide a few scenarios as to what they may be doing, and hope to provide a modicum of clarity.
Colloq flyer 4-6