ABSTRACT
SE V E N immunologically distinct neurotoxins (NTX), types A to G, are produced by Clostridium botulinum strains. The NTXs inhibit the release of acetylcholine (Ach) at the neuromuscular junctions and synapses, and cause botulism in humans and animals. Molecular mass (Mr) of all the types of NTXs is approximately 150 kDa. The NTXs associate with nontoxic components in cultures, and become large complexes that are designated progenitor toxins. Recently, the genes coding for type A to G NTXs have been cloned, and their entire nucleotide sequences determined. Furthermore, it has become clear that the NTXs are Zn+ +-binding proteins and possess protease activity. The structure and function of the nontoxic components of the progenitor toxins have also been investigated.
