9vcs
Cryo-EM structure of semi-closed state of Botulinum neurotoxin serotype A at pH 7.4
Structural highlights
FunctionBXA1_CLOBH Inhibits acetylcholine release. The botulinum toxin binds with high affinity to peripheral neuronal presynaptic membrane to the secretory vesicle protein SV2. It binds directly to the largest luminal loop of SV2A, SV2B and SV2C. It is then internalized by receptor-mediated endocytosis. The C-terminus of the heavy chain (H) is responsible for the adherence of the toxin to the cell surface while the N-terminus mediates transport of the light chain from the endocytic vesicle to the cytosol. After translocation, the light chain (L) hydrolyzes the 197-Gln-|-Arg-198 bond in SNAP-25, thereby blocking neurotransmitter release. Inhibition of acetylcholine release results in flaccid paralysis, with frequent heart or respiratory failure. Publication Abstract from PubMedBotulinum neurotoxin type A (BoNT/A) has been extensively used in treating a wide range of neurological disorders and aesthetics. However, insufficient binding affinity between BoNT/A and its receptor SV2C could lead to mild to severe side effects. An open active conformation of BoNT/A cryo-EM structure at a resolution of approximately 2.85 A was resolved. Guided by the BoNT/A cryo-EM structure, saturation mutagenesis libraries were constructed and screened by BACTH system to identify mutants that can boost toxin-SV2C affinity. The engineered toxin binding domain achieved up to approximately six-fold improved affinity in SPR analysis, and the engineered toxins exhibited significantly improved binding capacity, and enhanced SNAP25 cleavage efficacy in cultured neurons. Preclinical animal studies, including MLB, DAS, sweat test, and PET/CT assays, demonstrated that the engineered BoNT/A VLTS has higher potency, lower diffusion, and significantly better safety profiles than the BoNT/A wt, which can reduce side effects and benefit future therapeutic applications. Cryo-EM Structure Guided Engineering of Botulinum Neurotoxin A With Advanced Receptor Binding Affinity and Therapeutical Benefits.,Wang W, Zerang Z, You L, Liu Z, Nie R, Qi F, Gao F, Zhao C, Ma W, He J, Wang X, Wu S, Liu B, Liu X, Lei D, Zhi D, Wang D Adv Sci (Weinh). 2026 Apr 7:e16713. doi: 10.1002/advs.202516713. PMID:41944347[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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