Interactions of antibiotic peptides with lipid membranes

用光谱和热分析技术研究了几种抗菌肽与脂膜的相互作用，以阐明它们的作用机理。我们发现了以下内容。1.疏水性海藻糖素和毛霉菌素对卵磷脂具有通透性。菌丝素的膜亲和力和膜扰动活性均比毛霉素大3倍。这一发现很好地符合了菌丝素较强的溶血活性。我们的FTIR-ATR研究表明，这两种多肽都符合膜上的螺旋结构，深入穿透它们的疏水区域，破坏它们的脂质取向，使它们通透。相应地，膜相变消失。2.两亲性肌动蛋白与酸性脂双层特异性结合，形成两亲性螺旋，使膜通透性增强。静电相互作用是膜结合的重要因素。用色氨酸取代的类似物进行的荧光研究表明，麦芽凝集素以聚集形式存在于膜的浅层区域。此外，与母肽相比，截断的衍生物显示出类似的活性，表明C末端的5个残基对于活性来说是不必要的。3、具有两亲性的片状结构，与酸性磷脂特异性强结合，提高膜的通透性。进一步添加多肽聚集体、融合和胶束化100 nm大小的脂质体，形成直径10-20 nm的小颗粒。电荷中和似乎对小颗粒的形成很重要。凝胶状态下的双分子层比流体状态下的双分子层更容易受到这些形态变化的影响。唯一的色氨酸残基位于膜表面附近的疏水区。

Interactions of several antibiotic peptides with lipid membranes were investigated by using spectroscopic and thermal techniques to elucidate their action mechanisms. We found the followings. 1. Hydroprhobic hypelein and trichopolyn permeabilize lecithin membranes. Both membrane affinity and membrane-perturbing activity of hypelcin were three times larger than those of trichopolyn. This finding corresponds well to a stronger hemolytic activity of hypelcin. Our FTIR-ATR study revealed that both peptides conform to helices in membranes, deeply penetrating their hydrophobic region, disrupting their lipid orientation to permeabilize them. Correspondingly, the membrane phase transition disappears. 2. Amphilphilic magainins specifically interact with acidic lipid bilayers, forming amphiphilic helices to permeabilize the membranes. Electrostatic interactions are important for the membrane binding. A fluorescence study using tryptophan-substituted analogs shows that magainins lay in a shallow region of the membranes in an aggregated form. Furthermore, a truncated derivative shows a similar activity compared with the parent peptide, suggesting that the C-terminal five residues are unnecessary for the activity. 3. Tachyplesin, having an amphiphilic sheet structure, specifically and strongly bind to acidic phospholipids, enhancing the membrane permeability. Further addition of the peptide aggregates, fuse, and micellize 100 nm-sized liposomes, forming small particles of 10-20 nm in diameter. Charge neutralization seems to be important for the small particle formation. Bilayers in the gel state are more susceptible to these morphological changes than those in the fluid state. The unique tryptophan residue is located in a hydrophobic region near the membrane surface.