ANALYSIS OF THE BOTULINUM NEUROTOXIN TYPE-F GENE CLUSTERS IN PROTEOLYTIC AND NONPROTEOLYTIC CLOSTRIDIUM-BOTULINUM AND CLOSTRIDIUM-BARATI

Comparison of genes encoding type F botulinum neurotoxin progenitor co mplex in strains of proteolytic Clostridium botulinum strain Langeland , nonproteolytic Clostridium botulinum strain 202F, and Clostridium ba rati strain ATCC 43256 reveals an identical organization of genes enco ding a protein of molecular mass of approx. 47 kDa (P-47), nontoxic-no nhemagglutinin (NTNH) and botulinum toxin (BoNT). Although homology be tween the protein components of the complexes encoded by these differe nt species all producing botulinum neurotoxin type F is considerable ( approx. 69-88% identity), exceptionally high homology is observed betw een the C-termini of the P-47s (approx. 96% identity) and the NTNHs (a pprox. 94% identity) encoded by Clostridium botulinum type F strain La ngeland and Clostridium botulinum type A strain Kyoto. Such a region o f extremely high sequence identity is strongly indicative of recombina tion in these strains synthesizing botulinum neurotoxins of different antigenic types.