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Assembly of Staphy lococcus aureus alpha-toxin on target membranes

金黄色葡萄球菌α-毒素在靶膜上的组装

基本信息

批准号：
05670248
负责人：
TOMITA Toshio
金额：
$ 1.28万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

Staphylococcus aureus alpha-toxin is a 33-kDa polypeptide endowed with hemolytic, dermonecrotic and lethal activities. It is thought to bind to membranes, assemble into pore-forming hexamers, eventually causing colloid osmotic lysis of cells. Our previous studies showed that staphylococcal alpha-toxin binds specifically to the choline-type phospholipids, and that the increase in membrane fluidity promotes hexamerization of the toxin on target membranes. In this project, we prepared fragments of alpha-toxin and assayd their binding and pore-forming abilities. The results indicated (1) that several fragments, such as Alal-Glu71, Gly72-Asn293, Thr9-Lys131 and Ile132-Asn293 retained ability to bind to phosphatidylcholine-cholesterol liposomes and erythrocyte membranes, (2) that these fragments did not form membrane pores, although they assembled partially into dimers on the membranes, and (3) that a larger-sized fragment (Thr9-Asn293) showed little pore-forming activity towards liposomes and erythrocytes, although it retained the binding and oligomerizing abilities. These data suggest that both of the N-terminal and the C-terminal portions of alpha-toxin are indispensable for its pore-forming ability. Thus, our data are not consistent with the previous proposal that different domains of alpha-toxin are responsible for defferent functions (e.g., C-Terminal 18-kDa fragment of the toxin was reported to be hemolytic). Our results may suggest that monomer molecules of alpha-toxin are linked in a head-to-head manner when they assemble into hexamers.

金黄色葡萄球菌α-毒素是一种具有溶血、皮肤坏死和致死活性的33-kDa多肽。它被认为与细胞膜结合，组装成成孔形成六聚体，最终导致细胞的胶体渗透溶解。我们以前的研究表明，葡萄球菌α-毒素特异性结合胆碱型磷脂，膜流动性的增加，促进靶膜上的毒素的六聚化。在本项目中，我们制备了α-毒素的片段，并测定了它们的结合和成孔能力。结果表明：（1）Alal-Glu 71、Gly 72-Asn 293、Thr 9-Lys 131和Ile 132-Asn 293等片段保留了与磷脂酰胆碱-胆固醇脂质体和红细胞膜结合的能力;（2）这些片段虽然在膜上部分组装成二聚体，但不形成膜孔，（3）较大的片段（Thr 9-Asn 293）对脂质体和红细胞几乎没有致孔活性，但保留了结合和寡聚化能力。这些数据表明，α-毒素的N-末端和C-末端部分对于其孔形成能力是不可缺少的。因此，我们的数据与先前的假设不一致，即α-毒素的不同结构域负责不同的功能（例如，据报告，该毒素的C-末端18-kDa片段具有溶血性）。我们的研究结果可能表明，单体分子的α-毒素是连接在一个头对头的方式时，他们组装成六聚体。