There is growing concern on fusion efficiency of proteoliposome (PL) as it is vital for the reconstitution of ion channels into artificial lipid bilayer. Recently, we discovered the formation of microdomains on a ternary lipid bilayer consisting of egg-derived phosphatidylcholine (PC), phosphatidylethanolamine (PE) and cholesterol (Chol) which function as specific fusion site for PL. In general, phase separation occurs in ternary lipid bilayers containing Chol and partially miscible lipids such as dipalmitoyl and dioleoyl PCs. However, in this study we used egg-derived PC and PE which are both in liquid crystalline phase and are both completely miscible without Chol. Formation of domains in completely miscible lipid bilayers after additional of Chol is an exceptional phenomenon. For that, we investigated the composition of this unique microdomain formation. Based on our discovery on microdomains, we proposed that increment in the area fraction of microdomains by manipulating the composition and concentration of lipid bilayers will ultimately lead to increment in fusion efficiency of PL. In this study, we investigated the effects of PE concentration (CPE) and types of PE on microdomains formation as PE assists the fusion of two bilayer membranes due to their intrinsic negative curvature. We prepared PC+PE+Chol-SLBs using egg-derived and synthetic PEs at = 67−CPE:CPE:33:0.26 (molar ratio). The increment in CPE facilitated the formation of planar SLBs from vesicles and increased the area fraction of microdomains (θ). Microdomains were in liquid-disordered-like state and PE-rich. PE with polyunsaturated chains such as the docosahexaenoyl group was the key factor of the microdomain formation. The results showed that PE with docosahexaenoyl group had the largest θ among egg-derived PE and dioleoyl-PE. The fusion efficiency of PL increased in the PC+PE+Chol-SLB containing docosahexaenoyl-PE.

Cholestrol-induced microdomains formation in completely miscible lipid bilayers which promotes the fusion of proteoliposome

2019 Spring National Meeting

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