Blasi J, Chapman E R, Link E, Binz T, Yamasaki S, De Camilli P, Südhof T C, Niemann H, Jahn R
Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06510.
Nature. 1993 Sep 9;365(6442):160-3. doi: 10.1038/365160a0.
Neurotransmitter release is potently blocked by a group of structurally related toxin proteins produced by Clostridium botulinum. Botulinum neurotoxin type B (BoNT/B) and tetanus toxin (TeTx) are zinc-dependent proteases that specifically cleave synaptobrevin (VAMP), a membrane protein of synaptic vesicles. Here we report that inhibition of transmitter release from synaptosomes caused by botulinum neurotoxin A (BoNT/A) is associated with the selective proteolysis of the synaptic protein SNAP-25. Furthermore, isolated or recombinant L chain of BoNT/A cleaves SNAP-25 in vitro. Cleavage occurred near the carboxyterminus and was sensitive to divalent cation chelators. In addition, a glutamate residue in the BoNT/A L chain, presumably required to stabilize a water molecule in the zinc-containing catalytic centre, was required for proteolytic activity. These findings demonstrate that BoNT/A acts as a zinc-dependent protease that selectively cleaves SNAP-25. Thus, a second component of the putative fusion complex mediating synaptic vesicle exocytosis is targeted by a clostridial neurotoxin.
肉毒杆菌产生的一组结构相关的毒素蛋白可有效阻断神经递质的释放。肉毒杆菌B型神经毒素（BoNT/B）和破伤风毒素（TeTx）是锌依赖性蛋白酶，它们特异性切割突触小泡的膜蛋白突触小泡蛋白（VAMP）。在此我们报告，肉毒杆菌A型神经毒素（BoNT/A）引起的突触体神经递质释放抑制与突触蛋白SNAP-25的选择性蛋白水解有关。此外，BoNT/A的分离或重组轻链在体外可切割SNAP-25。切割发生在羧基末端附近，并且对二价阳离子螯合剂敏感。另外，BoNT/A轻链中的一个谷氨酸残基可能是在含锌催化中心稳定水分子所必需的，它是蛋白水解活性所必需的。这些发现表明，BoNT/A作为一种锌依赖性蛋白酶，可选择性切割SNAP-25。因此，介导突触小泡胞吐作用的假定融合复合物的第二个组分被一种梭菌神经毒素靶向作用。
