Surface aggregation and membrane penetration by peptides: relation to pore formation and fusion
Surface aggregation and membrane penetration by peptides: relation to pore formation and fusion
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DOI：
10.1080/096876899294814
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发表时间：
1999-01-01
影响因子：
--
通讯作者：
Szoka, FC
中科院分区：
文献类型：
--
作者：
Nir, S;Nicol, F;Szoka, FC
当 pH 值降低时，肽 GALA 会发生构象变化，形成两亲性 α 螺旋，从而导致囊泡内容物泄漏。 pH 5.0 时中性或带负电的囊泡的泄漏是相似的，并且可以通过数学模型充分解释，该数学模型假设 GALA 融入囊泡双层并不可逆地聚集形成由 M=10+/-2 肽组成的孔。膜中胆固醇含量的增加导致渗漏减少，并且肽表面聚集的可逆性增加。采用荧光标记的肽证实，GALA表面聚集的可逆性程度在含有胆固醇的脂质体中显着更大。通过 bodipy-亲和素/生物素结合测定确定肽 GALA 在双层中的方向。该肽在 N 或 C 末端用生物素标记，并在外部添加 bodipy-avidin 分子或预封装在囊泡中。肽在孔中垂直于膜排列，使得 3/4 的 N 末端位于膜的内侧。毛孔稳定并持续至少 10 分钟。当肽形成尺寸小于M的聚集体时，肽的方向大部分平行于表面并且生物素化的肽不会易位。当聚集体达到临界尺寸时，肽会发生重排，这相当于快速渗透并形成孔结构。肽诱导融合可能会对抗孔的形成，其结果取决于囊泡聚集。
The peptide GALA undergoes a conformational change to an amphipathic alpha-helix when the pH is reduced, inducing leakage of contents from vesicles. Leakage from neutral or negatively-charged vesicles at pH 5.0 was similar and could be adequately explained by a mathematical model which assumed that GALA becomes incorporated into the vesicle bilayer and irreversibly aggregates to form a pore consisting of M=10+/-2 peptides. Increasing cholesterol content in the membranes resulted in reduced leakage, and increased reversibility of surface aggregation of the peptide, Employing fluorescently labelled peptides confirmed that the degree of reversibility of surface aggregation of GALA was significantly larger in cholesterol containing liposomes. Orientation of the peptide GALA in bilayers was determined by a bodipy-avidin/biotin binding assay. The peptide was labelled by biotin at the N- or C-terminus and bodipy-avidin molecules were added externally or were preencapsulated in the vesicles. The peptides are arranged in the pore perpendicularly to the membrane, such that 3/4 of the N-termini are on the internal side of the membrane. The pores are stable and persist for at least 10 min. When the peptides form an aggregate of size smaller than M, the orientation of the peptide is mostly parallel to the surface and the biotinylated peptide does not translocate. When a critical size of the aggregate is attained, a rearrangement of the peptide occurs, which amounts to rapid penetration and formation of a pore structure. Induction of fusion by peptides may be antagonistic to pore formation, the outcome being dependent on vesicle aggregation.