Molecular construction of Clostridium botulinum type C progenitor toxin and its gene organization.

The 16S progenitor toxin of Clostridium botulinum type C is made up by conjugation of a neurotoxin with nontoxic components designated as nontoxic-nonHA and hemagglutinin (HA). The HA was found to be composed of subcomponents having 53, 33, 22-23, and 17 kDa molecular masses. Since we previously determined the whole nucleotide sequences of the genes for neurotoxin, nontoxic-nonHA, and HA-33, the cloning and nucleotide sequencing of the genes for the remaining HA subcomponents were performed. Two open reading frames coding for 16.7 kDa (HA-17) and 70.6 kDa proteins were identified. The N-terminal amino acid sequences of HA-53 and HA-22-23 indicated that the 70.6 kDa protein is split into 53 and the 22-23 kDa proteins after translation and that the 22-23 kDa protein consists of at least four proteins showing slightly different molecular weights.