Molecular characterization of two forms of nontoxic‐nonhemagglutinin components of Clostridium botulinum type A progenitor toxins

The entire sequences of the type A nontoxic-nonhemagglutinin gene and an adjacent open reading frame designated as orf 22-a, which are located between the neurotoxin and the HA-35 genes were determined. SDS-PAGE and N-terminal amino acid sequence analyses of the purified type A progenitor toxins (12S, 16S and 19S) indicate that the nontoxic-nonhemagglutinins of 16S and 19S are single peptides of approximately 120k, but that of 12S has a cleavage at the site between Pro-144 and Phe-145 of this protein.