Lipid Headgroup Spacing and Peptide Penetration, but Not Peptide Oligomerization, Modulate Peptide-Induced Fusion

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• 作者：Eve-Isabelle Pé ; cheur ; Josette Sainte-Marie ; Alain Bienvenü ; e ; and Dick Hoekstra
• 刊名：Biochemistry
• 出版年：1999
• 出版时间：January 5, 1999
• 年：1999
• 卷：38
• 期：1
• 页码：364 - 373
• 全文大小：145K
• 年卷期：v.38,no.1(January 5, 1999)
• ISSN：1520-4995

文摘

In this study, the mechanism by which an amphipathic negatively charged peptide consistingof 11 amino acids (WAE) induces fusion of liposomal phosphatidylcholine membranes is investigated.WAE-induced fusion, which only occurs when the peptide is covalently attached to the bilayer, shows ahighly remarkable dependence on naturally occurring phosphatidylcholine species. The initial rate of fusionincreased in the order 1-palmitoyl 2-arachidonoyl PC (PAPC) > 1-palmitoyl 2-oleoyl PC (POPC) >1-stearoyl 2-oleoyl PC (SOPC) > dioleoyl PC (DOPC) > egg yolk PC. Interestingly, the susceptibilityof the various PC species toward WAE-induced fusion matched a similar order of increase in intrinsiclipid headgroup spacing of the target membrane. The degree of spacing, in turn, was found to be relatedto the extent by which the fluorescence quantum yield of the Trp residue increased, which occurred uponthe interaction of WAE with target membranes. Therefore, these results demonstrate an enhanced abilityfor WAE to engage in hydrophobic interactions when headgroup spacing increases. Thus, this latterparameter most likely regulates the degree of penetration of WAE into the target membrane. Apart frompenetrating, WAE oligomerizes at the site of fusion as revealed by monitoring the self-quenching of thefluorescently derivatized lipid anchor to which WAE is attached. Clustering appears specifically relatedto the process of membrane fusion and not membrane aggregation. This is indicated by the fact thatfusion and clustering, but not aggregation, display the same strict temperature dependence. However,evidence is presented indicating that clustering is an accompanying event rather than a prerequisite forfusion. The notion that various biologically relevant fusion phenomena are accompanied by proteinclustering and the specific PC-species-dependent regulation of membrane fusion emphasize the biologicalsignificance of the peptide in serving as a model for investigating mechanisms of protein-induced fusion.