Kitamura A, Kiyota T, Tomohiro M, Umeda A, Lee S, Inoue T, Sugihara G
Department of Chemistry, Faculty of Science, Fukuoka University, Jonan-ku, Fukuoka 814-0180, Japan.
Biophys J. 1999 Mar;76(3):1457-68. doi: 10.1016/S0006-3495(99)77306-6.
Lipid-peptide interaction has been investigated using cationic amphiphilic alpha-helical peptides and systematically varying their hydrophobic-hydrophilic balance (HHB). The influence of the peptides on neutral and acidic liposomes was examined by 1) Trp fluorescence quenched by brominated phospholipid, 2) membrane-clearing ability, 3) size determination of liposomes by dynamic light scattering, 4) morphological observation by electron microscopy, and 5) ability to form planar lipid bilayers from channels. The peptides examined consist of hydrophobic Leu and hydrophilic Lys residues with ratios 13:5, 11:7, 9:9, 7:11, and 5:13 (abbreviated as Hels 13-5, 11-7, 9-9, 7-11, and 5-13, respectively; Kiyota, T., S. Lee, and G. Sugihara. 1996. Biochemistry. 35:13196-13204). The most hydrophobic peptide (Hel 13-5) induced a twisted ribbon-like fibril structure for egg PC liposomes. In a 3/1 (egg PC/egg PG) lipid mixture, Hel 13-5 addition caused fusion of the liposomes. Hel 13-5 formed ion channels in neutral lipid bilayer (egg PE/egg PC = 7/3) at low peptide concentrations, but not in an acidic bilayer (egg PE/brain PS = 7/3). The peptides with hydrophobicity less than Hel 13-5 (Hels 11-7 and Hel 9-9) were able to partially immerse their hydrophobic part of the amphiphilic helix in lipid bilayers and fragment liposome to small bicelles or micelles, and then the bicelles aggregated to form a larger assembly. Peptides Hel 11-7 and Hel 9-9 each formed strong ion channels. Peptides (Hel 7-11 and Hel 5-13) with a more hydrophilic HHB interacted with an acidic lipid bilayer by charge interaction, in which the former immerses the hydrophobic part in lipid bilayer, and the latter did not immerse, and formed large assemblies by aggregation of original liposomes. The present study clearly showed that hydrophobic-hydrophilic balance of a peptide is a crucial factor in understanding lipid-peptide interactions.
利用阳离子两亲性α-螺旋肽并系统地改变其疏水-亲水平衡（HHB），对脂质-肽相互作用进行了研究。通过以下方法检测了这些肽对中性和酸性脂质体的影响：1）溴化磷脂猝灭色氨酸荧光；2）膜清除能力；3）动态光散射法测定脂质体大小；4）电子显微镜形态观察；5）从通道形成平面脂质双层的能力。所检测的肽由疏水性亮氨酸和亲水性赖氨酸残基组成，比例分别为13:5、11:7、9:9、7:11和5:13（分别简称为Hels 13-5、11-7、9-9、7-11和5-13；Kiyota, T., S. Lee, and G. Sugihara. 1996. Biochemistry. 35:13196-13204）。疏水性最强的肽（Hel 13-5）诱导卵磷脂脂质体形成扭曲的带状纤维结构。在3/1（卵磷脂/蛋黄磷脂酰甘油）脂质混合物中，添加Hel 13-5会导致脂质体融合。Hel 13-5在低肽浓度下能在中性脂质双层（蛋黄磷脂酰乙醇胺/卵磷脂=7/3）中形成离子通道，但在酸性双层（蛋黄磷脂酰乙醇胺/脑磷脂酰丝氨酸=7/3）中则不能。疏水性小于Hel 13-5的肽（Hels 11-7和Hel 9-9）能够将其两亲性螺旋的疏水部分部分浸入脂质双层中，并将脂质体破碎成小的双分子层或胶束，然后双分子层聚集形成更大的聚集体。肽Hel 11-7和Hel 9-9各自形成强离子通道。具有更亲水HHB的肽（Hel 7-11和Hel 5-13）通过电荷相互作用与酸性脂质双层相互作用，其中前者将疏水部分浸入脂质双层中，而后者不浸入，并通过原始脂质体的聚集形成大的聚集体。本研究清楚地表明，肽的疏水-亲水平衡是理解脂质-肽相互作用的关键因素。
