Which toxin is produced by Clostridium botulinum and causes paralysis by blocking acetylcholine release?

Which toxin is produced by Clostridium botulinum and causes paralysis by blocking acetylcholine release?

• A. Diphtheria toxin
• B. Cholera toxin
• C. Tetanus toxin
• D. Botulinum toxin

Answer: (D)

Acetylcholine release at the neuromuscular junction is what triggers muscle contraction; botulinum toxin blocks this release by cleaving SNARE proteins needed for vesicle fusion, and the toxin’s light chain acts as a zinc-dependent protease that disrupts the vesicle fusion machinery. Without acetylcholine, motor neurons can’t stimulate the muscle, leading to flaccid paralysis. This distinguishes it from the other toxins: diphtheria toxin shuts down protein synthesis in cells; cholera toxin drives secretory diarrhea through increased cAMP; tetanus toxin blocks inhibitory neurotransmitter release, causing spastic, rigid paralysis. The toxin that stops acetylcholine release at the NMJ, producing flaccid paralysis, is botulinum toxin.