Transbilayer complementarity of phospholipids in cholesterol-rich membranes

Lipid-lipid interactions across cholesterol-rich phospholipid bilayers were investigated by measuring nearest-neighbor preferences of exchangeable phospholipids derived from 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine (DMPE) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE), in the presence of nonexchangeable dimers (i.e., templates) made from DMPE or DSPE. When homotemplates were present, a significant preference for homophospholipid association was observed. In contrast, when the corresponding heterotemplate was present, heterodimer formation was favored. These results support a model in which the longer phospholipid in one monolayer preferentially associates with the shorter one in the adjoining monolayer. In the absence of cholesterol, transbilayer complementarity was also observed but to a lesser degree. Transbilayer complementarity of phospholipids is likely to play an important role in stabilizing biological membranes and in promoting a compositional interdependence of their two lipid leaflets.