Kanellis P, Romans A Y, Johnson B J, Kercret H, Chiovetti R, Allen T M, Segrest J P
J Biol Chem. 1980 Dec 10;255(23):11464-72.
The amphipathic helix hypothesis for plasma lipoproteins was investigated using synthetic peptides. The lipid-associating properties of two potentially amphipathic model peptides and two analogs were studied by incubating synthetic peptides with small unilamellar vesicles and protein-lipid association examined by equilibrium density centrifugation, leakage of liposome-entrapped fluorescence compounds, intrinsic tryptophan fluorescence, and circular dichroism spectroscopy. The analog peptides were designed to determine the significance of the number and specific location of the charged residues in amphipathic domains of plasma lipoproteins to protein-lipid association. Based on the four procedures used to examine protein-lipid interactions, the two model peptides (18Aa, 18As) were found to associate strongly with liposomes; the two analog peptides (18As1, 18Asr), differing only with respect to the number and/or position of their charged residues, failed to demonstrate similar lipid binding properties. These findings support the earlier suggestions of the importance of the charged residues, but do not define the precise mechanisms involved. Such amino acids may help initiate the lipid-protein association by electrostatic interactions, contribute to the hydrophobicity of the nonpolar face of the helix by the acyl portion of lysine and arginine, and/or complement the charge distribution in the polar head regions of the phospholipid molecules.
利用合成肽对血浆脂蛋白的两亲性螺旋假说进行了研究。通过将合成肽与小单层囊泡孵育，研究了两种潜在的两亲性模型肽及其两种类似物与脂质结合的特性，并通过平衡密度离心、脂质体包裹的荧光化合物泄漏、色氨酸固有荧光和圆二色光谱法检测蛋白质-脂质结合情况。设计这些类似肽是为了确定血浆脂蛋白两亲结构域中带电残基的数量和特定位置对蛋白质-脂质结合的重要性。基于用于检测蛋白质-脂质相互作用的四种方法，发现两种模型肽（18Aa、18As）与脂质体强烈结合；而两种类似肽（18As1、18Asr），仅在带电残基的数量和/或位置上有所不同，未能表现出类似的脂质结合特性。这些发现支持了早期关于带电残基重要性的观点，但并未明确其中的确切机制。这些氨基酸可能通过静电相互作用帮助启动脂质-蛋白质结合，通过赖氨酸和精氨酸的酰基部分增加螺旋非极性面的疏水性，和/或补充磷脂分子极性头部区域的电荷分布。
