Arndt Joseph W, Yu Wayne, Bi Fay, Stevens Raymond C
Department of Molecular Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037, USA.
Biochemistry. 2005 Jul 19;44(28):9574-80. doi: 10.1021/bi0505924.
The seven serotypes (A-G) of botulinum neurotoxins (BoNTs) block neurotransmitter release through their specific proteolysis of one of the three proteins of the soluble N-ethylmaleimide-sensitive-factor attachment protein receptor (SNARE) complex. BoNTs have stringent substrate specificities that are unique for metalloprotease in that they require exceptionally long substrates (1). To understand the molecular reasons for the unique specificities of the BoNTs, we determined the crystal structure of the catalytic light chain (LC) of Clostridium botulinum neurotoxin type G (BoNT/G-LC) at 2.35 A resolution. The structure of BoNT/G-LC reveals a C-terminal beta-sheet that is critical for LC oligomerization and is unlike that seen in the other LC structures. Its structural comparison with thermolysin and the available pool of LC structures reveals important serotype differences that are likely to be involved in substrate recognition of the P1' residue. In addition, structural and sequence analyses have identified a potential exosite of BoNT/G-LC that recognizes a SNARE recognition motif of VAMP.
肉毒杆菌神经毒素（BoNTs）的七种血清型（A - G）通过对可溶性N - 乙基马来酰亚胺敏感因子附着蛋白受体（SNARE）复合物的三种蛋白质之一进行特异性蛋白水解来阻断神经递质释放。BoNTs具有严格的底物特异性，这对于金属蛋白酶来说是独特的，因为它们需要特别长的底物（1）。为了理解BoNTs独特特异性的分子原因，我们以2.35埃的分辨率确定了G型肉毒杆菌神经毒素（BoNT/G）催化轻链（LC）的晶体结构。BoNT/G - LC的结构揭示了一个对LC寡聚化至关重要的C端β - 折叠，这与其他LC结构中所见的不同。其与嗜热菌蛋白酶以及现有LC结构库的结构比较揭示了重要的血清型差异，这些差异可能与P1'残基的底物识别有关。此外，结构和序列分析确定了BoNT/G - LC的一个潜在外部位点，该位点识别VAMP的SNARE识别基序。
