Silvaggi Nicholas R, Boldt Grant E, Hixon Mark S, Kennedy Jack P, Tzipori Saul, Janda Kim D, Allen Karen N
Department of Physiology and Biophysics, Boston University School of Medicine, Boston, MA 02118, USA.
Chem Biol. 2007 May;14(5):533-42. doi: 10.1016/j.chembiol.2007.03.014.
The potential for the use of Clostridial neurotoxins as bioweapons makes the development of small-molecule inhibitors of these deadly toxins a top priority. Recently, screening of a random hydroxamate library identified a small-molecule inhibitor of C. botulinum Neurotoxin Serotype A Light Chain (BoNT/A-LC), 4-chlorocinnamic hydroxamate, a derivative of which has been shown to have in vivo efficacy in mice and no toxicity. We describe the X-ray crystal structures of BoNT/A-LC in complexes with two potent small-molecule inhibitors. The structures of the enzyme with 4-chlorocinnamic hydroxamate or 2,4-dichlorocinnamic hydroxamate bound are compared to the structure of the enzyme complexed with L-arginine hydroxamate, an inhibitor with modest affinity. Taken together, this suite of structures provides surprising insights into the BoNT/A-LC active site, including unexpected conformational flexibility at the S1' site that changes the electrostatic environment of the binding pocket. Information gained from these structures will inform the design and optimization of more effective small-molecule inhibitors of BoNT/A-LC.
梭菌神经毒素有被用作生物武器的潜在风险，这使得开发针对这些致命毒素的小分子抑制剂成为当务之急。最近，对一个随机异羟肟酸文库的筛选鉴定出了一种肉毒杆菌神经毒素A轻链（BoNT/A-LC）的小分子抑制剂——4-氯肉桂酸异羟肟酸，其一种衍生物已被证明在小鼠体内具有疗效且无毒性。我们描述了BoNT/A-LC与两种强效小分子抑制剂形成的复合物的X射线晶体结构。将结合了4-氯肉桂酸异羟肟酸或2,4-二氯肉桂酸异羟肟酸的酶结构与结合了L-精氨酸异羟肟酸（一种亲和力适中的抑制剂）的酶复合物结构进行了比较。综合来看，这一系列结构为BoNT/A-LC活性位点提供了惊人的见解，包括S1'位点意想不到的构象灵活性，这种灵活性改变了结合口袋的静电环境。从这些结构中获得的信息将为设计和优化更有效的BoNT/A-LC小分子抑制剂提供参考。
