Process of inducing pores in membranes by melittin
Process of inducing pores in membranes by melittin
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DOI：
10.1073/pnas.1307010110
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发表时间：
2013-08-27
影响因子：
11.1
通讯作者：
Huang, Huey W.
中科院分区：
文献类型：
--
作者：
Lee, Ming-Tao;Sun, Tzu-Lin;Huang, Huey W.
蜂毒素是一种无处不在的抗菌肽的原型，这种抗菌肽可以诱导膜上的毛孔。它通常用作膜通透性的分子装置。即使在纳摩尔浓度范围内，蜂毒素也可以诱导瞬间的毛孔，允许原子离子的跨膜传导，但不会泄漏葡萄糖或更大的分子。在微摩尔浓度下，蜂毒素诱导稳定的毛孔，使分子跨膜渗漏多达数万道尔顿，这与其抗菌活性相对应。尽管进行了广泛的研究，但孔洞形成的分子机制仍不清楚。为了阐明这一机制，必须了解蜂毒素结合膜在这一过程前后的状态。通过对大单层囊泡和肽脂多层膜的相关实验，我们发现结合在囊泡上的蜂毒素在形成稳定的孔之前移位和重新分布到膜的两侧。此外，只有在临界的肽脂比以上才能形成稳定的毛孔。瞬变和稳定毛孔的初始状态是不同的，这意味着在低和高肽浓度下的机制不同。为了确定膜孔的脂类结构，将多肽脂多层膜中的膜孔诱导成晶格，并用反常X射线衍射仪进行了观察。脂标记物的电子密度分布表明，孔是由两个界面通过一个孔合并而成的。蜂毒素的分子特性是它能强烈吸附在双层界面上。孔的形成可以看作是双层采用了类脂构型来适应其过大的界面面积。
Melittin is a prototype of the ubiquitous antimicrobial peptides that induce pores in membranes. It is commonly used as a molecular device for membrane permeabilization. Even at concentrations in the nanomolar range, melittin can induce transient pores that allow transmembrane conduction of atomic ions but not leakage of glucose or larger molecules. At micromolar concentrations, melittin induces stable pores allowing transmembrane leakage of molecules up to tens of kilodaltons, corresponding to its antimicrobial activities. Despite extensive studies, aspects of the molecular mechanism for pore formation remain unclear. To clarify the mechanism, one must know the states of the melittin-bound membrane before and after the process. By correlating experiments using giant unilamellar vesicles with those of peptide-lipid multilayers, we found that melittin bound on the vesicle translocated and redistributed to both sides of the membrane before the formation of stable pores. Furthermore, stable pores are formed only above a critical peptide-to-lipid ratio. The initial states for transient and stable pores are different, which implies different mechanisms at low and high peptide concentrations. To determine the lipidic structure of the pore, the pores in peptide-lipid multilayers were induced to form a lattice and examined by anomalous X-ray diffraction. The electron density distribution of lipid labels shows that the pore is formed by merging of two interfaces through a hole. The molecular property of melittin is such that it adsorbs strongly to the bilayer interface. Pore formation can be viewed as the bilayer adopting a lipid configuration to accommodate its excessive interfacial area.