Mancheño J M, Gasset M, Albar J P, Lacadena J, Martínez del Pozo A, Oñaderra M, Gavilanes J G
Departamento de Bioquímica y Biología Molecular, Facultad de Química, Universidad Complutense, Madrid, Spain.
Biophys J. 1995 Jun;68(6):2387-95. doi: 10.1016/S0006-3495(95)80421-2.
alpha-Sarcin is a cytotoxic protein that strongly interacts with acid phospholipid vesicles. This interaction exhibits a hydrophobic component although alpha-sarcin is a highly polar protein. A peptide comprising the amino acid sequence corresponding to the 116-139th segment of the alpha-sarcin cytotoxin has been synthesized by a standard fluoren-9-yl-methoxycarbonyl-based solid phase method. Its primary structure is: (116)-NPGPARVIYTYPNKVFCGIIAHTK-(139). Two beta-strands have been predicted in this region of alpha-sarcin, where the less polar stretches of the protein are found. The synthetic peptide interacts with negatively charged large unilamellar vesicles of either natural or synthetic phospholipids. An apparent fragmentation of the vesicles is produced by the peptide based on electron microscopy studies. The peptide promotes leakage of the intravesicular aqueous contents and lipid mixing of bilayers. The packing of the phospholipid molecules is greatly perturbed by the peptide, as deduced from the drastic changes induced by the peptide in cooperative properties associated with the phase transition of the bilayers. At saturating peptide/phospholipid ratios, the phase transition of dimyristoylphosphatidylglycerol vesicles is abolished. All of these effects are saturated at about 0.3 peptide/lipid molar ratio. The peptide adopts a mostly random structure in aqueous solution. A conformation composed of a high proportion of antiparallel beta-sheet is induced as a consequence of the interaction with the phospholipid vesicles in opposition to trifluoroethanol that promotes alpha-helical peptide structures, as deduced from circular dichroism measurements. The obtained results are discussed in terms of the potential involvement of the region comprising residues 116-139 of alpha-sarcin in the hydrophobic interactions of this cytotoxic protein with membranes.
α-肌动蛋白是一种细胞毒性蛋白，它与酸性磷脂囊泡强烈相互作用。尽管α-肌动蛋白是一种高度极性的蛋白，但这种相互作用表现出疏水成分。通过基于芴-9-基甲氧基羰基的标准固相方法合成了一种包含与α-肌动蛋白细胞毒素第116 - 139段相对应氨基酸序列的肽。其一级结构为：(116)-NPGPARVIYTYPNKVFCGIIAHTK-(139)。在α-肌动蛋白的该区域预测有两条β链，该蛋白极性较小的片段位于此处。合成肽与天然或合成磷脂的带负电荷的大单层囊泡相互作用。基于电子显微镜研究，该肽会导致囊泡出现明显的碎片化。该肽促进囊泡内水相内容物的泄漏以及双层膜的脂质混合。从该肽引起的与双层膜相变相关的协同性质的剧烈变化推断，磷脂分子的堆积受到该肽的极大干扰。在饱和的肽/磷脂比例下，二肉豆蔻酰磷脂酰甘油囊泡的相变被消除。所有这些效应在约0.3肽/脂质摩尔比时达到饱和。该肽在水溶液中大多呈随机结构。根据圆二色性测量推断，与促进α-螺旋肽结构的三氟乙醇相反，该肽与磷脂囊泡相互作用会诱导出由高比例反平行β-折叠组成的构象。根据α-肌动蛋白第116 - 139位残基区域在这种细胞毒性蛋白与膜的疏水相互作用中的潜在作用对所得结果进行了讨论。
