Interaction of diphtheria toxin and its active subunit, fragment A, with toxin-sensitive and toxin-resistant cells
Interaction of diphtheria toxin and its active subunit, fragment A, with toxin-sensitive and toxin-resistant cells
复制标题
白喉毒素及其活性亚基片段 A 与毒素敏感和毒素抗性细胞的相互作用
作者：
T. Moehring;J. Moehring
对白喉毒素及其活性亚基纯化片段A进行了毒素敏感型和通透型抗毒素培养哺乳动物细胞的检测。在敏感细胞和抗性细胞中，纯化片段a的活性浓度对蛋白质合成的抑制程度相同。相反，抗性细胞所需的全毒素浓度比敏感细胞所需的浓度高5至6倍，才能达到相同的抑制程度。在摩尔基础上，片段a的毒性相当于整个毒素对抗性细胞的毒性。这些结果证明毒素或其活性部分进入细胞存在两种独立的机制。一种机制是高效的毒素特异性进入机制，涉及表面受体和片段b介导的关联，并在敏感细胞中活跃。另一种是效率较低的非特异性机制，可能与内吞作用有关，它在敏感细胞和耐药细胞中起作用，但在敏感细胞暴露于全毒素时，由于特异性机制的作用而不明显。
Diphtheria toxin and purified fragment A, the active subunit of the toxin, were tested on toxin-sensitive and permeability class toxin-resistant cultured mammalian cells. Protein synthesis was inhibited to the same degree in sensitive or resistant cells by active concentrations of purified fragment A. In contrast, resistant cells required a concentration of whole toxin 5 to 6 logs greater than that required by sensitive cells to achieve the same degree of inhibition. On a molar basis, the toxicity of fragment A was equivalent to that of whole toxin on resistant cells. These results are evidence for the existence of two independent mechanisms for the entry of toxin or its active moiety into cells. One mechanism is a highly efficient, toxin-specific entry mechanism, involving surface receptor and fragment B-mediated association, and is active in sensitive cells. The other is a less efficient, nonspecific mechanism, probably related to endocytosis, which is operative in sensitive and resistant cells but is inapparent in sensitive cells when they are exposed to whole toxin because of the action of the specific mechanism.