Hanna P C, Wnek A P, McClane B A
Department of Microbiology, University of Pittsburgh School of Medicine, Pennsylvania 15261.
J Bacteriol. 1989 Dec;171(12):6815-20. doi: 10.1128/jb.171.12.6815-6820.1989.
Clostridium perfringens type A enterotoxin (CPE) causes the symptoms associated with C. perfringens food poisoning. To determine whether the C-terminal half of CPE contains receptor-binding activity, the 3' half of the cpe structural gene was cloned with an Escherichia coli expression vector system. E. coli lysates containing the expressed C-terminal CPE fragment (CPEfrag) were then assayed for CPE-like serologic, receptor-binding, and cytotoxic activities. CPEfrag was shown to contain an epitope located at or near the receptor-binding domain of the CPE molecule. Competitive-binding studies showed specific competition for CPE receptors between CPE and CPEfrag lysates. CPEfrag lysates did not cause cytotoxicity in Vero (African green monkey kidney) cells. However, preincubation with CPEfrag lysates specifically protected Vero cells from subsequent CPE challenge. This indicates that CPEfrag recognizes the physiologic receptor which mediates CPE cytotoxicity. Collectively, these studies indicate that the C-terminal half of CPE contains a receptor-binding domain but additional amino acid sequences appear to be required for CPE cytotoxicity.
A型产气荚膜梭菌肠毒素（CPE）会引发与产气荚膜梭菌食物中毒相关的症状。为了确定CPE的C端一半是否具有受体结合活性，利用大肠杆菌表达载体系统克隆了cpe结构基因的3'端一半。然后对含有表达的C端CPE片段（CPEfrag）的大肠杆菌裂解物进行CPE样血清学、受体结合和细胞毒性活性检测。结果显示CPEfrag含有一个位于CPE分子受体结合域或其附近的表位。竞争性结合研究表明，CPE与CPEfrag裂解物之间对CPE受体存在特异性竞争。CPEfrag裂解物对非洲绿猴肾细胞（Vero细胞）无细胞毒性。然而，用CPEfrag裂解物进行预孵育可特异性保护Vero细胞免受后续CPE攻击。这表明CPEfrag识别介导CPE细胞毒性的生理受体。总体而言，这些研究表明CPE的C端一半含有一个受体结合域，但CPE细胞毒性似乎还需要其他氨基酸序列。
