Miyake M, Ohishi I
University of Osaka Prefecture, College of Agriculture, Japan.
Microb Pathog. 1987 Oct;3(4):279-86. doi: 10.1016/0882-4010(87)90061-1.
C2 toxin (C2T) elaborated by Clostridium botulinum types C and D is composed of two nonlinked protein components, designated components I and II. The toxin, a mixture of untrypsinized component I and trypsinized component II, induced marked morphological changes of tissue-cultured cynomolgus monkey kidney cells; the characteristic response of the cells to the toxin was rounding, which increased proportionally to log dose of the toxin. The components alone and a combination of untrypsinized components I and II showed little activity. The rounding of the cultured cells was not accompanied by inhibition of protein and nucleic acid syntheses of the cells, although the rounded cells ultimately lost viability. Immunofluorescence studies showed that component II, either trypsinized or untrypsinized, bound to the cell surface, whereas component I bound to the cells only in the presence of trypsinized component II. The present results support the previously proposed idea concerning the mode of action of C2T, that components I and II of C2T act together as a molecule with dual functions; component II as the recognizer of the receptor site on the cell surface membranes and component I as the effector in the cytoplasm by preferential inactivation of cytoskeletal actin, which results in alteration of cell morphology, and subsequently in cellular damage.
由C型和D型肉毒杆菌产生的C2毒素（C2T）由两种非连接的蛋白质成分组成，分别称为成分I和成分II。该毒素是未胰蛋白酶处理的成分I和经胰蛋白酶处理的成分II的混合物，可诱导组织培养的食蟹猴肾细胞发生明显的形态变化；细胞对该毒素的特征性反应是变圆，且与毒素的对数剂量成比例增加。单独的成分以及未胰蛋白酶处理的成分I和II的组合显示出很少的活性。培养细胞的变圆并不伴随着细胞蛋白质和核酸合成的抑制，尽管变圆的细胞最终会失去活力。免疫荧光研究表明，经胰蛋白酶处理或未处理的成分II都能与细胞表面结合，而成分I只有在存在经胰蛋白酶处理的成分II时才能与细胞结合。目前的结果支持了先前提出的关于C2T作用方式的观点，即C2T的成分I和成分II作为具有双重功能的分子共同起作用；成分II作为细胞表面膜上受体位点的识别者，成分I作为细胞质中的效应器，通过优先使细胞骨架肌动蛋白失活，导致细胞形态改变，随后造成细胞损伤。
