ASSOCIATION OF A PH-SENSITIVE PEPTIDE WITH MEMBRANE-VESICLES - ROLE OF AMINO-ACID-SEQUENCE
ASSOCIATION OF A PH-SENSITIVE PEPTIDE WITH MEMBRANE-VESICLES - ROLE OF AMINO-ACID-SEQUENCE
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DOI：
10.1021/bi00489a030
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发表时间：
1990-09-18
期刊：
影响因子：
2.9
通讯作者：
SZOKA, FC
中科院分区：
文献类型：
--
作者：
PARENTE, RA;NADASDI, L;SZOKA, FC
研究了人工合成的两种30个氨基酸的多肽GALA和LAGA在pH值为5和7.5时的溶液性质和双层缔合作用。这些多肽具有相同的氨基酸组成，唯一不同的是谷氨酸和亮氨酸残基的位置，这两个残基加起来占每个多肽的47%。当pH从7.5降低到5.0时，两种多肽都经历了类似的螺旋到螺旋的转变。然而，Gala形成两亲性α-螺旋，而Laga不形成。因此，GALA比LAGA更大程度地进入膜中，并可启动LAGA所不能的囊泡内容物的泄漏和膜融合(Subarao等人，1987；Parente等人，1988)。用大的磷脂酰胆碱小泡详细研究了多肽的膜结合作用。直接结合测量表明，在pH为5时，多肽Gala与囊泡有很强的结合，表观Ka约为106。每个多肽中的单一色氨酸残基可以被用来探测多肽在脂双层中的运动和定位。各向异性的变化和溴化脂质在囊泡存在下对色氨酸荧光的猝灭也表明GALA可以以一种pH依赖的方式与未带电的囊泡相互作用。通过与多肽LAGA的比较，GALA的膜结合被证明是由于其在pH为5时的α-螺旋构象的两亲性。
The solution properties and bilayer association of two synthetic 30 amino acid peptides, GALA and LAGA, have been investigated at pH 5 and 7.5. These peptides have the same amino acid composition and differ only in the positioning of glutamic acid and leucine residues which together compose 47% of each peptide. Both peptides undergo a similar coil to helix transition as the pH is lowered from 7.5 to 5.0. However, GALA forms an amphipathic .alpha.-helix whereas LAGA does not. As a result, GALA partitions into membranes to a greater extent than LAGA and can initiate leakage of vesicle contents and membrane fusion which LAGA cannot (Subbarao et al., 1987; Parente et al., 1988). Membrane association of the peptides has been studied in detail with large phosphatidylcholine vesicles. Direct binding measurements show a strong association of the peptide GALA to vesicles at pH 5 with an apparent Ka around 106. The single tryptophan residue in each peptide can be exploited to a probe peptide motion and positioning within lipid bilayers. Anisotropy changes and the quenching of tryptophan fluorescence by brominated lipids in the presence of vesicles also indicate that GALA can interact with uncharged vesicles in a pH-dependent manner. By comparison to the peptide LAGA, the membrane association of GALA is shown to be due to the amphipathic nature of its .alpha.-helical conformation at pH 5.