What is the name of the protein in Botulinum (Clostridium botulinum) toxin?

From the Guidelines

The protein in botulinum toxin is called botulinum neurotoxin (BoNT), a zinc-endopeptidase protein consisting of a heavy chain and a light chain, as described in the 2021 clinical guidelines for diagnosis and treatment of botulism 1. This protein is produced by the bacterium C. botulinum and exists in seven distinct serotypes labeled A through G.

• The mechanism of action of botulinum neurotoxin involves binding to a neuronal cell, internalization, translocation to the cytosol, and cleavage of proteins involved in the release of the neurotransmitter acetylcholine, leading to flaccid paralysis 1.
• The protein's structure and function are crucial to its therapeutic applications, such as in products like Botox, where it is used to achieve localized muscle relaxation without systemic effects.
• The different serotypes of botulinum neurotoxin (A, B, C, D, E, F, and G) have varying levels of potency and effects on human disease, with type A producing the most severe syndrome 1. The use of botulinum neurotoxin in medical applications requires careful consideration of its potential benefits and risks, as well as strict control over dosage and administration to minimize adverse effects.
• The clinical guidelines for diagnosis and treatment of botulism provide valuable information on the pathophysiology, diagnosis, and management of botulism, including the use of botulinum neurotoxin as a therapeutic agent 1.

From the FDA Drug Label

PrabotulinumtoxinA-xvfs is a 900 kDa botulinum toxin type A, produced from fermentation of Clostridium botulinum The protein in botulinum toxin is botulinum toxin type A, also known as prabotulinumtoxinA-xvfs 2.

• The botulinum toxin type A is a neurotoxin complex.
• It is produced from fermentation of Clostridium botulinum.

From the Research

Protein Structure of Botulinum Toxin

• The botulinum toxin is a 150-kDa protein toxin organized into heavy chain (HC) and light chain (LC) domains linked by a disulfide bond 3.
• The heavy chain (HC) domain of the botulinum toxin is responsible for binding to neurons and aiding cell entry of the enzymatically active light chain (LC) 3, 4.
• The light chain (LC) domain of the botulinum toxin is a zinc-endopeptidase that cleaves one or two among three synaptic proteins (VAMP-synaptobrevin, SNAP25, and syntaxin) 3, 4, 5.

Specific Proteins in Botulinum Toxin

• The light chain (LC) of botulinum neurotoxin type A is a 50 kDa protein that cleaves at a single glutaminyl-arginine bond corresponding to residues 197 and 198 at the C-terminus of SNAP25 5.
• The heavy chain (HC) of botulinum neurotoxin type A is a 100 kDa protein that comprises the receptor binding and translocation domains 5.

Functions of the Proteins

• The light chain (LC) of the botulinum toxin defines the duration of action of the toxin 3.
• The heavy chain (HC) and light chain (LC) of the botulinum toxin work together to block acetylcholine release, causing dysautonomia and motor paralysis 4.