Bergey G K, Habig W H, Bennett J I, Lin C S
Department of Neurology, University of Maryland School of Medicine, Baltimore 21201.
J Neurochem. 1989 Jul;53(1):155-61. doi: 10.1111/j.1471-4159.1989.tb07307.x.
Tetanus toxin is initially synthesized in the form of a single polypeptide chain and then proteolytically "nicked" by the bacteria to produce a two-chain structure joined by a disulfide bond. This two-chain form of the toxin is the form known to be biologically active. Whether such nicking is necessary for activity, as it is for certain other bacterial toxins, has not been demonstrated previously. Single-chain toxin preparations produced by salt extraction from the bacteria are characterized and compared with pure two-chain toxin obtained from extracellular filtrates. The ability of these various toxin preparations to produce paroxysmal activity in mouse spinal cord neurons grown in dissociated cell culture is described. The pure two-chain toxin is demonstrated to have greater activity than the single-chain toxin preparations. Indeed the activity of the single-chain toxin preparations can be explained by the small amounts of residual two-chain toxin present in these extracts. Using a protease from a toxin-minus strain of Clostridium tetani to convert a single-chain toxin preparation to two-chain toxin increases toxin activity. In vivo the single-chain toxin preparation is also less toxic. These findings indicate that proteolytic nicking of tetanus toxin increases activity. The unnicked, single-chain form of tetanus toxin may be a relatively nontoxic protoxin form of the toxin; this is a structure-function relationship similar to that of other bacterial protein toxins.
破伤风毒素最初以单条多肽链的形式合成，然后被细菌进行蛋白水解“切割”，产生由二硫键连接的双链结构。这种双链形式的毒素是已知具有生物活性的形式。此前尚未证实这种切割对于活性是否像某些其他细菌毒素那样是必需的。对通过从细菌中盐提取制备的单链毒素制剂进行了表征，并与从细胞外滤液中获得的纯双链毒素进行了比较。描述了这些各种毒素制剂在解离细胞培养中生长的小鼠脊髓神经元中产生阵发性活动的能力。已证明纯双链毒素比单链毒素制剂具有更高的活性。实际上，单链毒素制剂的活性可以用这些提取物中存在的少量残留双链毒素来解释。使用来自破伤风梭菌毒素缺失菌株的蛋白酶将单链毒素制剂转化为双链毒素会增加毒素活性。在体内，单链毒素制剂的毒性也较小。这些发现表明破伤风毒素的蛋白水解切割会增加活性。未切割的单链形式的破伤风毒素可能是该毒素相对无毒的前体毒素形式；这是一种与其他细菌蛋白毒素类似的结构 - 功能关系。
