Integrated Bioscience Section, Graduate School of Science and Technology , Shizuoka University , Shizuoka 422-8529 , Japan.
Theoretical Problem Center of Physico-Chemical Pharmacology , Russian Academy of Sciences , Kosugina, 4 , 117977 Moscow , Russia.
Langmuir. 2018 Mar 13;34(10):3349-3362. doi: 10.1021/acs.langmuir.7b04219. Epub 2018 Feb 27.
Antimicrobial peptide magainin 2 forms pores in lipid bilayers, a property that is considered the main cause of its bactericidal activity. Recent data suggest that tension or stretching of the inner monolayer plays an important role in magainin 2-induced pore formation in lipid bilayers. Here, to elucidate the mechanism of magainin 2-induced pore formation, we investigated the effect on pore formation of asymmetric lipid distribution in two monolayers. First, we developed a method to prepare giant unilamellar vesicles (GUVs) composed of dioleoylphosphatidylglycerol (DOPG), dioleoylphosphatidylcholine (DOPC), and lyso-PC (LPC) in the inner monolayer and of DOPG/DOPC in the outer monolayer. We consider that in these GUVs, the lipid packing in the inner monolayer was larger than that in the outer monolayer. Next, we investigated the interaction of magainin 2 with these GUVs with an asymmetric distribution of LPC using the single GUV method, and found that the rate constant of magainin 2-induced pore formation, k, decreased with increasing LPC concentration in the inner monolayer. We constructed a quantitative model of magainin 2-induced pore formation, whereby the binding of magainin 2 to the outer monolayer of a GUV induces stretching of the inner monolayer, causing pore formation. A theoretical equation defining k as a function of magainin 2 surface concentration, X, reasonably explains the experimental relationship between k and X. This model quantitatively explains the effect on k of the LPC concentration in the inner monolayer. On the basis of these results, we discuss the mechanism of the initial stage of magainin 2-induced pore formation.
抗菌肽magainin 2 在脂质双层中形成孔，这种性质被认为是其杀菌活性的主要原因。最近的数据表明，内层的张力或拉伸在magainin 2 诱导的脂质双层中孔形成中起着重要作用。在这里，为了阐明 magainin 2 诱导孔形成的机制，我们研究了内层不对称脂质分布对孔形成的影响。首先，我们开发了一种方法来制备由二油酰基磷脂酰甘油（DOPG）、二油酰基磷脂酰胆碱（DOPC）和溶磷脂酰胆碱（LPC）组成的内单层和 DOPG/DOPC 组成的大单分子层囊泡（GUVs）。我们认为在这些 GUVs 中，内层的脂质堆积大于外层。接下来，我们使用单分子层囊泡方法研究了具有不对称 LPC 分布的这些 GUVs 中 magainin 2 的相互作用，并发现 magainin 2 诱导的孔形成的速率常数 k 随着内层中 LPC 浓度的增加而降低。我们构建了 magainin 2 诱导孔形成的定量模型，其中 magainin 2 与 GUV 的外层结合诱导内层拉伸，导致孔形成。一个定义 k 为 magainin 2 表面浓度 X 的函数的理论方程合理地解释了 k 与 X 之间的实验关系。该模型定量解释了内层中 LPC 浓度对 k 的影响。基于这些结果，我们讨论了 magainin 2 诱导孔形成的初始阶段的机制。
