Botulinum neurotoxin B recognizes its protein receptor with high affinity and specificity
Botulinum neurotoxin B recognizes its protein receptor with high affinity and specificity
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DOI：
10.1038/nature05387
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发表时间：
2006-12-21
期刊：
影响因子：
64.8
通讯作者：
Brunger, Axel T.
中科院分区：
文献类型：
--
作者：
Jin, Rongsheng;Rummel, Andreas;Brunger, Axel T.
肉毒杆菌神经毒素（BoNT）是由肉毒梭菌产生的，可引起肉毒中毒的神经麻痹综合征。其致死剂量为1 ng/kg（-1），对人类构成生物危害，并构成严重的潜在生物武器威胁（1）。BoNT在神经肌肉接头处以高特异性结合，并且它们通过SNARE（可溶性N-乙基马来酰亚胺敏感性融合蛋白附着蛋白受体）的特异性蛋白水解损害含有乙酰胆碱的突触囊泡的胞吐作用，所述SNARE构成突触囊泡融合机制的一部分（2，3）。毒素-细胞识别的分子细节一直难以捉摸。在这里，我们报告的结构的肉毒杆菌毒素与其蛋白受体的复合物：受体结合结构域的肉毒杆菌神经毒素血清型B（肉毒杆菌毒素/B）结合的突触结合蛋白II的腔域，在2.15埃的分辨率。在结合时，在管腔结构域中诱导螺旋，其结合BoNT/B的远端尖端上的鞍形裂缝。该裂隙邻近BoNT/B的非重叠神经节苷脂结合位点。突触结合蛋白II与BoNT/B相互作用与纳摩尔亲和力，在中性和酸性内体pH值。生化和神经元离体研究的结构为基础的突变表明高特异性和亲和力的相互作用，和高选择性的BoNT/B之间的突触结合蛋白I和II亚型。synaptotagmin和神经节苷脂的协同结合对内吞作用后BoNT/B易位的起始施加几何限制。我们的研究结果为合理开发针对这些神经毒素的预防性疫苗或抑制剂提供了基础。
Botulinum neurotoxins (BoNTs) are produced by Clostridium botulinum and cause the neuroparalytic syndrome of botulism. With a lethal dose of 1 ng kg(-1), they pose a biological hazard to humans and a serious potential bioweapon threat(1). BoNTs bind with high specificity at neuromuscular junctions and they impair exocytosis of synaptic vesicles containing acetylcholine through specific proteolysis of SNAREs (soluble N-ethylmaleimide-sensitive fusion protein attachment protein receptors), which constitute part of the synaptic vesicle fusion machinery(2,3). The molecular details of the toxin-cell recognition have been elusive. Here we report the structure of a BoNT in complex with its protein receptor: the receptor-binding domain of botulinum neurotoxin serotype B (BoNT/B) bound to the luminal domain of synaptotagmin II, determined at 2.15 angstrom resolution. On binding, a helix is induced in the luminal domain which binds to a saddle-shaped crevice on a distal tip of BoNT/B. This crevice is adjacent to the non-overlapping ganglioside-binding site of BoNT/B. Synaptotagmin II interacts with BoNT/B with nanomolar affinity, at both neutral and acidic endosomal pH. Biochemical and neuronal ex vivo studies of structure-based mutations indicate high specificity and affinity of the interaction, and high selectivity of BoNT/B among synaptotagmin I and II isoforms. Synergistic binding of both synaptotagmin and ganglioside imposes geometric restrictions on the initiation of BoNT/B translocation after endocytosis. Our results provide the basis for the rational development of preventive vaccines or inhibitors against these neurotoxins.