Benachir T, Lafleur M
Département de Chimie, Université de Montréal, Québec, Canada.
Biochim Biophys Acta. 1995 May 4;1235(2):452-60. doi: 10.1016/0005-2736(95)80035-e.
The leakage induced by melittin, a membrane-perturbing amphipathic peptide, from large unilamellar 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) vesicles was studied using calcein as fluorescent marker. The extent of leakage has been found to be regulated by the melittin/lipid molar ratio. Melittin leads to the complete release of trapped calcein from some vesicles. This all-or-none mechanism leads to the co-existence of two different vesicle populations: the 'empty' and the intact one. Intervesicular migration of melittin was not observed. The results reveal a specific targeting of the lysed vesicles by melittin. The presence of negatively charged lipids (unprotonated palmitic acid or 1-palmitoyl-2-oleoylphosphatidylglycerol) in the neutral POPC matrix inhibits the lytic power of melittin; this inhibition increases with increasing surface charge density. It is proposed that the anchorage of the peptide on the charged surface prevents the formation of defects allowing leakage. A statistical model based on a random distribution of the peptide molecules on the vesicles is proposed to describe the release induced by melittin. It is proposed that about 250 melittin molecules per vesicle are required to affect the bilayer permeability and to empty a vesicle of its content. This large number suggests that leakage is more likely due to collective membrane perturbation by the peptide rather than to the formation of a well-defined pore.
使用钙黄绿素作为荧光标记，研究了膜扰动性两亲肽蜂毒素诱导的大单层1-棕榈酰-2-油酰磷脂酰胆碱（POPC）囊泡泄漏。已发现泄漏程度受蜂毒素/脂质摩尔比调节。蜂毒素会导致一些囊泡中捕获的钙黄绿素完全释放。这种全或无机制导致两种不同囊泡群体共存：“空的”和完整的囊泡。未观察到蜂毒素的囊泡间迁移。结果揭示了蜂毒素对破裂囊泡的特异性靶向作用。中性POPC基质中带负电荷的脂质（未质子化的棕榈酸或1-棕榈酰-2-油酰磷脂酰甘油）的存在会抑制蜂毒素的裂解能力；这种抑制作用随着表面电荷密度的增加而增强。有人提出，肽在带电表面的锚定可防止形成允许泄漏的缺陷。提出了一种基于肽分子在囊泡上随机分布的统计模型来描述蜂毒素诱导的释放。有人提出，每个囊泡大约需要250个蜂毒素分子来影响双层通透性并清空囊泡内容物。这个庞大的数字表明，泄漏更可能是由于肽对膜的集体扰动，而不是由于形成明确的孔。
