Hendon R A, Tu A T
Biochim Biophys Acta. 1979 May 23;578(1):243-52. doi: 10.1016/0005-2795(79)90132-6.
The major toxin (crotoxin) of Crotalus durissus terrificus (neotropical rattlesnake) is known to be a reversible non-covalently associated complex consisting of an acidic and basic subunit. On separation biological activity is found only with the basic subunit, yet, although void of detectable biological activity, the acidic subunit is essential for the full neurotoxic activity of the complex. Recent evidence suggests that crotoxin A serves as a 'chaperone' to enhance the specificity of crotoxin B and, upon binding, crotoxin A is released to the medium. This study was designed to test this hypothesis. Dimethyl suberimidate, a bifunctional cross-linking agent, was used to irreversibly bind the two subunits. Disc electrophoresis, ion-exchange chromatography, molecular sieve chromatography, capillary isotachophoresis and isoelectric precipitation confirm the existence of an inter-subunit covalently cross-linked complex. The conversion of a dissociable complex to a non-dissociable complex abolished neurotoxicity. Although neurotoxicity was lost, phospholipase A2 (phosphatide 2-acyl-hydrolase, EC 3.1.1.4), which is found associated with many presynaptic neurotoxins, was unaffected. The data in this paper add credence to the 'chaperone' concept of crotoxin A and the importance of the reversible nature of the complex for full expression of neurotoxicity.
众所周知，热带响尾蛇（Crotalus durissus terrificus）的主要毒素（响尾蛇毒素）是一种由酸性和碱性亚基组成的可逆非共价结合复合物。分离后发现只有碱性亚基具有生物活性，然而，尽管酸性亚基没有可检测到的生物活性，但它对于复合物的完全神经毒性活性至关重要。最近的证据表明，响尾蛇毒素A作为一种“伴侣蛋白”来增强响尾蛇毒素B的特异性，并且在结合后，响尾蛇毒素A被释放到介质中。本研究旨在验证这一假设。使用双功能交联剂亚胺基二琥珀酸二甲酯将两个亚基不可逆地结合。圆盘电泳、离子交换色谱、分子筛色谱、毛细管等速电泳和等电沉淀证实了亚基间共价交联复合物的存在。可解离复合物向不可解离复合物的转化消除了神经毒性。虽然神经毒性丧失，但与许多突触前神经毒素相关的磷脂酶A2（磷脂2-酰基水解酶，EC 3.1.1.4）不受影响。本文的数据为响尾蛇毒素A的“伴侣蛋白”概念以及复合物的可逆性质对神经毒性充分表达的重要性提供了支持。
