Cloning of the structural gene for Clostridium botulinum type C1 toxin and whole nucleotide sequence of its light chain component.

The toxigenicity of Clostridium botulinum type C1 is mediated by specific bacteriophages. DNA was extracted from one of these phages. Two DNA fragments, 3 and 7.8 kb, which produced the protein reacting with antitoxin serum were cloned by using bacteriophage lambda gt11 and Escherichia coli. Both DNA fragments were then subcloned into pUC118 plasmids and transferred into E. coli cells. The nucleotide sequences of the cloned DNA fragments were analyzed by the dideoxy chain termination method, and their gene products were analyzed by Western immunoblot. The 7.8-kb fragment coded for the entire light chain component and the N terminus of the heavy chain component of the toxin, whereas the 3-kb fragment coded for the remaining heavy chain component. The entire nucleotide sequence for the light chain component was determined, and the derived amino acid sequence was compared with that of tetanus toxin. It was found that the light chain component of C1 toxin possessed several amino acid regions, in addition to the N terminus, that were homologous to tetanus toxin.