志贺毒素B亚基具有自身组装功能

利用基因工程表达的志贺毒素Ｂ亚基纯化产物研究志贺毒素的分子组装机理。首先对ＳｔｘＢ进行了分离纯化，并将蛋白质纯品溶解在磷酸缓冲液中。利用蛋白质交联的方法证实，在磷酸缓冲液体系中 ＳｔｘＢ可以自发聚合为不同的分子结构形式（单体至五聚体），并可以与游离和细胞膜表面的受体结合，对志贺毒素全毒素的细胞毒性有竞争抑制作用。结果表明，在没有Ａ亚基存在的情况下，单独的ＳｔｘＢ也可以自发组装为多聚体，说明ＳｔｘＢ具有自身组装的能力。

Assembly of shiga toxin B subunit in vitro

Molecular assembling mechanism of Shiga toxin was studied in vitro using its ex- pressed and purified B subunit(StxB). Results of protein cross-linking in vitro indicated that the B subunit could auto-assembly as varities from 1B to 5B stochiometry in phosphate-buffered saline(PBS). Gb3-ELISA result shown that the purified StxB could bind Gb3,the receptor of shi- ga toxin. On cultured HeLa cell, StxB could bind Gb3 and inhibate cytotoxity of shiga toxin. All results shown that StxB could auto-assembly as functional 5B structure without participation of shiga toxin A subunit in vitro.