Botulinum neurotoxin type A1 (BoNT/A1)

Botulinum neurotoxin A1 (BoNT/A1) is a highly potent zinc-dependent metalloprotease produced by the bacterium Clostridium botulinum and is the primary causative agent of botulism, a severe paralytic illness. The toxin functions through a multi-step process involving high-affinity binding to synaptic vesicle protein 2 (SV2) and gangliosides on peripheral cholinergic nerve terminals, followed by endocytosis and translocation of its light chain into the neuronal cytosol. Once inside, the light chain selectively cleaves the SNARE protein SNAP-25, which prevents the fusion of acetylcholine-containing vesicles with the presynaptic membrane. This action effectively blocks neurotransmitter release at the neuromuscular junction, leading to flaccid paralysis. Despite its extreme toxicity, BoNT/A1 is widely utilized as a therapeutic agent for various conditions, including muscle spasticity, chronic migraine, and hyperhidrosis, as well as for cosmetic facial treatments. Clinical management of intoxication relies on antitoxins that neutralize the toxin in the bloodstream, while research continues into small-molecule inhibitors that can target the toxin's enzymatic activity within the neuronal cytosol.

Other names

Botulinum toxin type AClostridium botulinum neurotoxin type ABontoxilysin-AOnabotulinumtoxinAAbobotulinumtoxinAIncobotulinumtoxinAPrabotulinumtoxinADaxibotulinumtoxinALetibotulinumtoxinA

BoNT/A1 acts as a zinc-dependent endopeptidase that selectively cleaves the synaptosome-associated protein 25 (SNAP-25). This cleavage prevents the formation of the SNARE complex required for the fusion of synaptic vesicles with the presynaptic membrane, thereby inhibiting the release of the neurotransmitter acetylcholine at the neuromuscular junction and other cholinergic synapses.