STAPHYLOCOCCAL ALPHA-TOXIN INCREASES THE PERMEABILITY OF LIPID VESICLES BY CHOLESTEROL-DEPENDENT AND PH-DEPENDENT ASSEMBLY OF OLIGOMERIC CHANNELS
STAPHYLOCOCCAL ALPHA-TOXIN INCREASES THE PERMEABILITY OF LIPID VESICLES BY CHOLESTEROL-DEPENDENT AND PH-DEPENDENT ASSEMBLY OF OLIGOMERIC CHANNELS
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DOI：
10.1111/j.1432-1033.1989.tb14790.x
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发表时间：
1989-05-15
期刊：
影响因子：
--
通讯作者：
MENESTRINA, G
中科院分区：
文献类型：
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作者：
FORTI, S;MENESTRINA, G
α-毒素是由金黄色葡萄球菌分泌的一种致死性溶血毒素，在脂膜上形成大尺寸的离子通道。为了研究通道组装的机制，我们研究了小单层囊泡上孔形成的动力学。我们已经使用了两种测定囊泡透化：一个是释放的荧光分子被困在他们的内室;另一个是施加的电位耗散。这两种方法表明，动力学是复杂的，由一个初始延迟，然后是一个非线性松弛。孔形成速率和透化程度对毒素/囊泡比的依赖性表明4-10个预插入的毒素单体的聚集是通道组装的基础。透化的pH依赖性表明毒素的酸性基团的质子化是通道形成的先决条件。在靶囊泡中包含胆固醇增强了α-毒素的影响，以剂量依赖性的方式，可能是通过促进其质子化。的位置上的两个相邻的天冬氨酸残基在位置127和128的毒素单体的质子结合位点的建议。
.alpha.-Toxin, a lethal hemolytic toxin secreted by Staphylococcus aureus, forms ionic channels of large size in lipid membranes. To investigate the mechanism of channel assembly we have studied the kinetics of pore formation on small unilamellar vesicles. We have used two assays of vesicle permeabilization: one is the release of a fluorescent molecule trapped in their inner compartment; the other is the dissipation of an imposed potential. Both methods indicate that the kinetics are complex consisting of an initial delay followed by a non-linear relaxation. The dependence of the pore formation rate and the extent of permeabilization on the toxin/vesicle ratio indicates that aggregation of 4-10 preinserted toxin monomers underlies channel assembly. The pH dependence of permeabilization suggests that protonation of an acidic group of the toxin is a prerequisite to channel formation. Inclusion of cholesterol in the target vesicles potentiates .alpha.-toxin effects, in a dose-dependent way, possibly by facilitating its protonation. The location of the proton-binding site on the two adjacent aspartic acid residues in positions 127 and 128 of the toxin monomer is proposed.