Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2021 Feb 20;22(1):1–10. doi: 10.7181/acfs.2021.00003

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

Copyright © 2021 The Korean Cleft Palate-Craniofacial Association

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

PMC Copyright notice

Fig. 1. — Mechanism of action of botulinum toxin (a four-step process). Step 1: after botulinum toxin is activated by proteolytic cleavage of the polypeptide chain into a 100 kDa heavy chain (Hc) and a 50 kDa light chain (Lc), linked by a disulphide bond (S-S); the Hc domain of the toxin binds to the presynaptic plasma membrane of the motor axon terminal. Step 2: the toxin complex is then internalized by energy-dependent endocytosis. Step 3: the Lc, a zinc endopeptidase, is released into the cytoplasm. Step 4: the Lc cleaves various components of SNARE (indicated by vertical arrows), including SNAP 25 (botulinum toxin A), VAMP/synaptobrevin (botulinum toxin B), or syntaxin (botulinum toxin C), and thus prevents the fusion of the acetylcholine synaptic vesicle with the plasma membrane. This blocks the release of the neurotransmitter into the synaptic cleft, causing local chemodenervation. SNARE, soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptor; SNAP, synaptosome associated protein; VAMP, vesicle-associated membrane protein; BTX, botulinum toxin. Reprinted from Jankovic. J Neurol Neurosurg Psychiatry 2004;75:951-7 [17].