Characterization of component-I gene of botulinum C2 toxin and PCR detection of its gene in clostridial species.

Botulinum C2 toxin is composed of two nonlinked protein components, component-I (light chain) and component-II (heavy chain). It is produced by Clostridium botulinum types C and D, and is thought to play a lethal pathogenic role. These biological activities of C2 toxin may be due to the ADP-ribosylation of non-muscle actin by component-I of the toxin. We were able to isolate two overlapping gene fragments encoding component-I from the chromosomal DNA of Clostridium botulinum type C strain (C)-203U28, and determine the complete nucleotide sequence of component-I gene. The gene for component-I, bc21, consists of one open reading frame (ORF) encoding 431 amino acid residues (1293 nucleotides) without signaling peptide sequence. The molecular mass calculated from the deduced amino acid sequence was 49400.37 Da. Mono-ADP-ribosyltransferase activity was demonstrated in the lysate from E. coli transformed by the recombinant plasmid, pGEM-C2 encompassing whole component-I gene with its own promoter.