Conformations and Dynamic Transitions of a Melittin Derivative That Forms Macromolecule-Sized Pores in Lipid Bilayers
Conformations and Dynamic Transitions of a Melittin Derivative That Forms Macromolecule-Sized Pores in Lipid Bilayers
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DOI：
10.1021/acs.langmuir.8b00804
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发表时间：
2018-07-17
期刊：
影响因子：
3.9
通讯作者：
King, Gavin M.
中科院分区：
文献类型：
--
作者：
Pittman, Anna E.;Marsh, Brendan P.;King, Gavin M.
MelP5是从蜂毒的主要活性成分系统进化而来，是一种亲脂肽，具有不同于野生型蜂毒素的重要物理特性，包括在低肽脂比下在脂质双层中产生大的平衡孔的能力。自组装成稳定的膜跨越孔使MelP5成为未来在制药领域应用的有希望的候选者。尽管有很大的兴趣，但对于MelP5在结合时重塑脂质双分子层的机制知之甚少。我们通过直接原子力显微镜对溶液中支持的脂质双分子层成像证明，MelP5以两种方式之一重塑了1-棕榈酰-2-油基- sin -甘油-3-磷脂胆碱（POPC）。它在双层中产生高度局部的空洞或漫漫性的非局部变薄。测量双分子层的变薄在双分子层上部小叶表面以下3.0 +/- 1.4埃（平均+/-标准差）。孔隙被定义为双分子层中高度局域化的空隙，具有不同的大小。大约20%的孔隙表现出较大的足迹面积（47 +/- 20 nm(2)），似乎能够通过大块的大分子。观察到多肽影响的双分子层在膜薄状态和孔状态之间以明显的动态平衡可逆地交换。对延时图像的分析表明，在膜变薄状态和孔隙状态之间转变的特征时间尺度上有上界和下界（0.2 < tau < 180 s）。此外，孔隙被发现与膜薄区域共定位，这一新的观察结果与形成孔隙时膜结合肽之间的协同性的概念一致。
Systematically evolved from the primary active component of bee venom, MelP5 is a lipophilic peptide with important physical properties that differ from wild-type melittin, including the ability to create large equilibrium pores in lipid bilayers at low peptide to lipid ratios. Self-assembly into stable membrane spanning pores makes MelP5 a promising candidate for future applications in the pharmaceutical arena. Despite significant interest, little is known about the mechanism by which MelP5 remodels the lipid bilayer upon binding. We demonstrate by direct atomic force microscope imaging of supported lipid bilayers in solution that MelP5 remodels 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in one of two ways. It creates either highly localized voids in the bilayer or diffuse nonlocalized thinning. Thinning of the bilayer was measured to be 3.0 +/- 1.4 angstrom (mean +/- standard deviation) below the surface of the upper leaflet of the bilayer. Pores, defined as highly localized voids in the bilayer, exhibited several sizes. Approximately 20% of pores exhibited large footprint areas (47 +/- 20 nm(2)) which appear capable of passing bulky macromolecules. The peptide-effected bilayer was observed to reversibly exchange between membrane-thinned and pore states in an apparent dynamic equilibrium. Analysis of time-lapsed images suggested upper and lower bounds (0.2 < tau < 180 s) on the characteristic time scale of transitions between the membrane-thinned and pore states. Moreover, pores were found to colocalize with membrane-thinned regions, a novel observation that is consistent with the notion of cooperativity among membrane-bound peptides when forming pores.