Membrane Bending Moduli of Coexisting Liquid Phases Containing Transmembrane Peptide.
Membrane Bending Moduli of Coexisting Liquid Phases Containing Transmembrane Peptide.
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DOI：
10.1016/j.bpj.2018.03.026
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发表时间：
2018-05
影响因子：
3.4
通讯作者：
R. D. Usery;T. A. Enoki;S. Wickramasinghe;V. Nguyen;David G. Ackerman;D. Greathouse;R. Koeppe;F. Barrera;G. Feigenson
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文献类型：
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作者：
R. D. Usery;T. A. Enoki;S. Wickramasinghe;V. Nguyen;David G. Ackerman;D. Greathouse;R. Koeppe;F. Barrera;G. Feigenson
体内许多高度弯曲的膜，例如上皮细胞微绒毛，具有与“筏状”成分相关的相对较高的鞘脂含量。考虑到具有“非筏”低鞘磷脂和低胆固醇含量的双层的弯曲能量要低得多，观察到可能更刚性的组合物的高曲率似乎是违反直觉的。为了理解这种行为，我们通过巨型单层囊泡的波动分析来测量膜刚性。我们发现，包含跨膜螺旋 GWALP 肽会增加液体无序 (Ld) 相的膜弯曲模量。我们观察到低胆固醇分数和更高、更生理性的胆固醇分数都有这种增加。我们发现简化的常用 Ld 相和液序 (Lo) 相不能代表共存相。当 Ld 和 Lo 相共存时，GWALP 肽有利于 Ld 相，分配系数为 3-10，具体取决于混合物组成。在高胆固醇分数的模型膜中，具有 GWALP 的 Ld 相比共存的 Lo 相具有更大的弯曲模量。
A number of highly curved membranes in vivo, such as epithelial cell microvilli, have the relatively high sphingolipid content associated with "raft-like" composition. Given the much lower bending energy measured for bilayers with "nonraft" low sphingomyelin and low cholesterol content, observing high curvature for presumably more rigid compositions seems counterintuitive. To understand this behavior, we measured membrane rigidity by fluctuation analysis of giant unilamellar vesicles. We found that including a transmembrane helical GWALP peptide increases the membrane bending modulus of the liquid-disordered (Ld) phase. We observed this increase at both low-cholesterol fraction and higher, more physiological cholesterol fraction. We find that simplified, commonly used Ld and liquid-ordered (Lo) phases are not representative of those that coexist. When Ld and Lo phases coexist, GWALP peptide favors the Ld phase with a partition coefficient of 3–10 depending on mixture composition. In model membranes at high cholesterol fractions, Ld phases with GWALP have greater bending moduli than the Lo phase that would coexist.