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Figure 2: Botulinum toxin consists of a heavy and light chain. After injection into the muscle, it reaches the neuromuscular junction where tissue proteases cleave the molecule into heavy and light chain. The heavy chain helps in internalization of the toxin by binding to nerve terminal surface glycoprotein receptors. The light chain impairs the binding of the SNARE (soluble N-ethyl maleimide-sensitive factor [NSF], attachment receptors, proteins essential for regulated exocytosis)/VAMP (vesicle associated membrane protein) with the synaptic vesicle containing acetylcholine and further prevents its fusion with the membrane. This inhibits the release of acetylcholine at the junction, and thereby, the muscle cannot contract. This results in muscle weakness. Different botulinum toxins target separate SNARE proteins as illustrated in the figure above

Figure 2: Botulinum toxin consists of a heavy and light chain. After injection into the muscle, it reaches the neuromuscular junction where tissue proteases cleave the molecule into heavy and light chain. The heavy chain helps in internalization of the toxin by binding to nerve terminal surface glycoprotein receptors. The light chain impairs the binding of the SNARE (soluble N-ethyl maleimide-sensitive factor [NSF], attachment receptors, proteins essential for regulated exocytosis)/VAMP (vesicle associated membrane protein) with the synaptic vesicle containing acetylcholine and further prevents its fusion with the membrane. This inhibits the release of acetylcholine at the junction, and thereby, the muscle cannot contract. This results in muscle weakness. Different botulinum toxins target separate SNARE proteins as illustrated in the figure above