Partitioning of Dual-Lipidated Peptides into Membrane Microdomains: Lipid Sorting vs Peptide Aggregation

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• 作者：Sascha Janosch ; Chiara Nicolini ; Bjö ; rn Ludolph ; Carsten Peters ; Martin Vö ; lkert ; Theodore L. Hazlet ; Enrico Gratton ; Herbert Waldmann ; and Roland Winter
• 刊名：Journal of the American Chemical Society
• 出版年：2004
• 出版时间：June 23, 2004
• 年：2004
• 卷：126
• 期：24
• 页码：7496 - 7503
• 全文大小：989K
• 年卷期：v.126,no.24(June 23, 2004)
• ISSN：1520-5126

文摘

The lateral membrane organization and phase behavior of the lipid mixture DMPC(di-C₁₄)/DSPC(di-C₁₈)/cholesterol (0-33 mol %) with and without an incorporated fluorescence-labeled palmitoyl/farnesyldual-lipidated peptide, BODIPY-Gly-Cys(Pal)-Met-Gly-Leu-Pro-Cys(Far)-OMe, which represents a membranerecognition model system for Ras proteins, was studied by two-photon excitation fluorescence microscopy.Measurements were performed on giant unilamellar vesicles (GUVs) over a large temperature range, rangingfrom 30 to 80 C to cover different lipid phase states (all-gel, fluid/gel, liquid-ordered, all-fluid). At temperatureswhere the fluid-gel coexistence region of the pure binary phospholipid system occurs, large-scaleconcentration fluctuations appear. Incorporation of cholesterol levels up to 33 mol % leads to a significantincrease of conformational order in the membrane system and a reduction of large domain structures.Adding the peptide leads to dramatic changes in the lateral organization of the membrane. With cholesterolpresent, a phase separation is induced by a lipid sorting mechanism owing to the high affinity of the lipidatedpeptide to a fluid, DMPC-rich environment. This phase separation leads to the formation of peptide-containingdomains with high fluorescence intensity that become progressively smaller with decreasing temperature.As a result, the local concentration of the peptide increases steadily within the confines of the shrinkingdomains. At the lowest temperatures, where the acyl-chain order parameter of the membrane has alreadydrastically increased and the membrane achieves a liquid-ordered character, an efficient lipid sortingmechanism is no longer supported and aggregation of the peptide into small clusters prevails. We canconclude that palmitoyl/farnesyl dual-lipidated peptides do not associate with liquid-ordered or gel-likedomains in phase-separated bilayer membranes. In particular, the study shows the interesting ability ofthe peptide to induce formation of fluid microdomains at physiologically relevant cholesterol concentrations,and this effect very much depends on the concentration of fluid vs ordered lipid molecules.