Percot A, Zhu X X, Lafleur M
Département de chimie, Université de Montréal, C. P. 6128, succursale Centre-ville, Montréal, Québec H3C 3J7, Canada.
Biopolymers. 1999 Nov;50(6):647-55. doi: 10.1002/(SICI)1097-0282(199911)50:6<647::AID-BIP9>3.0.CO;2-T.
In an effort to develop a polymer/peptide assembly for the immobilization of lipid vesicles, we have made and characterized four water-soluble amphiphilic peptides designed to associate spontaneously and strongly with lipid vesicles without causing significant leakage from anchored vesicles. These peptides have a primary amphiphilic structure with the following sequences: AAAAAAAAAAAAWKKKKKK, AALLLAAAAAAAAAAAAAAAAAAAWKKKKKK, and KKAALLLAAAAAAAAAAAAAAAAAAAWKKKKKK and its reversed homologue KKKKKKWAAAAA AAAAAAAAAAAAAALLLAAKK. Two of the four peptides have their hydrophobic segments capped at both termini with basic residues to stabilize the transmembrane orientation and to increase the affinity for negatively charged vesicles. We have studied the secondary structure and the membrane affinity of the peptides as well as the effect of the different peptides on the membrane permeability. The influence of the hydrophobic length and the role of lysine residues were clearly established. First, a hydrophobic segment of 24 amino acids, corresponding approximately to the thickness of a lipid bilayer, improves considerably the affinity to zwitterionic lipids compared to the shorter one of 12 amino acids. The shorter peptide has a low membrane affinity since it may not be long enough to adopt a stable conformation. Second, the presence of lysine residues is essential since the binding is dominated by electrostatic interactions, as illustrated by the enhanced binding with anionic lipids. The charges at both ends, however, prevent the peptide from inserting spontaneously in the bilayer since it would involve the translocation of a charged end through the apolar core of the bilayer. The direction of the amino acid sequence of the peptide has no significant influence on its behavior. None of these peptides perturbs membrane permeability even at an incubation lipid to peptide molar ratio of 0.5. Among the four peptides, AALLLAAAAAAAAAAAAAAAAAAAWKKKKKK is identified as the most suitable anchor for the immobilization of lipid vesicles.
为了开发一种用于固定脂质囊泡的聚合物/肽组装体，我们制备并表征了四种水溶性两亲性肽，这些肽被设计为能自发且强烈地与脂质囊泡结合，同时不会导致锚定囊泡出现明显渗漏。这些肽具有如下序列的一级两亲性结构：AAAAAAAAAAAAAAWKKKKKK、AALLLAAAAAAAAAAAAAAAAAAWKKKKKK、KKAALLLAAAAAAAAAAAAAAAAAAWKKKKKK及其反向同源物KKKKKKWAAAAA AAAAAAAAAAAAAALLLAAKK。四种肽中的两种在其疏水片段的两端都带有碱性残基封端，以稳定跨膜方向并增加对带负电荷囊泡的亲和力。我们研究了这些肽的二级结构和膜亲和力，以及不同肽对膜通透性的影响。明确确定了疏水长度的影响和赖氨酸残基的作用。首先，与12个氨基酸的较短疏水片段相比，约对应于脂质双层厚度的24个氨基酸的疏水片段能显著提高对两性离子脂质的亲和力。较短的肽具有较低的膜亲和力，因为它可能不够长，无法形成稳定的构象。其次，赖氨酸残基的存在至关重要，因为结合主要由静电相互作用主导，与阴离子脂质结合增强就说明了这一点。然而，两端的电荷会阻止肽自发插入双层膜，因为这将涉及带电端穿过双层膜的非极性核心的转运。肽的氨基酸序列方向对其行为没有显著影响。即使在脂质与肽的孵育摩尔比为0.5时，这些肽也不会干扰膜通透性。在这四种肽中，AALLLAAAAAAAAAAAAAAAAAAWKKKKKK被确定为固定脂质囊泡的最合适锚定物。
