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33 kDA多肽，含有溶血性，皮肤分析和致命活性。人们认为它与膜结合，组装成形成孔的六聚体，最终导致细胞的胶体渗透裂解。我们先前的研究表明，葡萄球菌α-毒素特异性与胆碱型磷脂，并且膜流动性的增加促进了毒素在靶膜上的六聚化。在这个项目中，我们准备了α-毒素的片段，并分析了它们的结合和孔形成能力。结果表明（1）几个片段，例如Alal-Glu71，Gly72-ASN293，Thr9-Lys131和Ile132-Asn293保留与磷脂酰胆碱 - 胆固醇 - 胆固醇脂质体脂质体和这些形成embranes embranes的磷脂酰胆碱 - 胆固醇 - 胆固醇 - （2）的能力，（2）尽管孔部分组装成膜上的二聚体，并且（3）较大尺寸的片段（THR9-ASN293）几乎没有对脂质体和红细胞的孔形成活性，尽管它保留了结合和低聚能力。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都是必不可少的。因此，我们的数据与先前的提议不一致，即α-毒素的不同域是负责功能的原因（例如，据报道毒素的C末端18-kDa片段是溶血性的）。我们的结果可能表明，α-毒素的单体分子在组装到己糖中时以正面方式连接。