Role of metals in the biological activity of clostridium botulinum neurotoxins
Role of metals in the biological activity of clostridium botulinum neurotoxins
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DOI：
10.1021/bi035844k
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发表时间：
2004-03-02
期刊：
影响因子：
2.9
通讯作者：
Swaminathan, S
中科院分区：
文献类型：
--
作者：
Eswaramoorthy, S;Kumaran, D;Swaminathan, S
肉毒杆菌神经毒素是对人类最有效的毒素，通过阻止突触前神经末梢的神经递质释放而导致瘫痪。毒性涉及四个步骤，即与神经元细胞结合、内化、易位和催化活性。虽然催化活性是 SNARE 复合体蛋白上的锌内肽酶活性，但易位被认为是 pH 依赖性过程，允许易位结构域改变其构象以穿透内体膜。在这里，我们报道了不同 pH 值下 B 型肉毒杆菌神经毒素和神经毒素 apo 形式的晶体结构，并讨论了金属离子的作用以及 pH 变化对生物活性的影响。除了一些侧链的扰动外，贫锌质朴毒素中催化结构域的构象没有改变，这表明锌的作用是催化作用。我们还鉴定了分子中的两个钙离子，并提供生化证据表明它们在轻链穿过膜的易位中发挥作用。
Clostridium botulinum neurotoxins are the most potent toxins to humans and cause paralysis by blocking neurotransmitter release at the presynaptic nerve terminals. The toxicity involves four steps, viz., binding to neuronal cells, internalization, translocation, and catalytic activity. While the catalytic activity is a zinc endopeptidase activity on the SNARE complex proteins, the translocation is believed to be a pH-dependent process allowing the translocation domain to change its conformation to penetrate the endosomal membrane. Here, we report the crystal structures of botulinum neurotoxin type B at various pHs and of an apo form of the neurotoxin, and discuss the role of metal ions and the effect of pH variation in the biological activity. Except for the perturbation of a few side chains, the conformation of the catalytic domain is unchanged in the zinc-depleted apotoxin, suggesting that zinc's role is catalytic. We have also identified two calcium ions in the molecule and present biochemical evidence to show that they play a role in the translocation of the light chain through the membrane.