EFFECT OF N-ACYL-PHOSPHATIDYLETHANOLAMINE ON THE MEMBRANE-FUSION BETWEEN SENDAI VIRUS AND LIPOSOME

We have compared the properties of two N-acyl derivatives of dilauryl phosphatidylethanolamine on lipid polymorphism, vesicle leakage and Se ndai virus fusion. The derivatives contained either an N-lauroyl group (NLPE) or an N-acetyl group (NAcPE). Only the NAcPE markedly affected the bilayer to hexagonal transition temperature of dielaidoyl phospha tidylethanolamine, shifting it to higher values. In contrast the NLPE slightly lowered this phase transition temperature. The two lipids als o have opposite effects on leakage from small unilamellar vesicles of egg phosphatidylcholine. The NLPE inhibits leakage, while the NAcPE pr omotes it. This vesicle stabilizing effect of NLPE against leakage is not manifested in alterations of rates or extents of Sendai virus fusi on to liposomes of egg phosphatidylethanolamine plus 2% ganglioside G( D1a). The NLPE has no effect, while the NAcPE reduces the observed fus ion, at least in part as a consequence of a reduction in the final ext ent of fusion. These results demonstrate that the bilayer stabilizing effects of NLPE do not result in a lower rate of viral fusion. Further more, these bilayer stabilizing effects against leakage are not solely a function of the lipid headgroup but also require a structure with t hree long acyl chains. The reduced leakage is not related to a loss in monolayer curvature strain.