MOLECULAR CHARACTERIZATION OF THE CLUSTERS OF GENES ENCODING THE BOTULINUM NEUROTOXIN COMPLEX IN CLOSTRIDIUM-BOTULINUM (CLOSTRIDIUM-ARGENTINENSE) TYPE-G AND NONPROTEOLYTIC CLOSTRIDIUM-BOTULINUM TYPE-B

The cluster of genes encoding components of the progenitor botulinum n eurotoxin complex has been mapped and cloned in Clostridium botulinum type G strain ATCC 27322. Determination of the nucleotide sequence of the region has revealed open reading frames encoding nontoxic componen ts of the complex, upstream of the gene encoding BoNT/G (botG). The ar rangement of these genes differs from that in strains of other antigen ic toxin types. Immediately upstream of botG lies a gene encoding a pr otein of 1198 amino acids, which shows homology with the nontoxic-nonh emagglutinin (NTNH) component of the progenitor complex. Further upstr eam there are genes encoding proteins with homology to hemagglutinin c omponents (HA-17, HA-70) and a putative positive regulator of gene exp ression (P-21). Sequence comparison has shown that BoNT/G has highest homology with BoNT/B. The sequence of the BoNT-cluster of genes in non -proteolytic C. botulinum type B strain Eklund 17B has been extended t o include the complete NTNH and HA-17, and partial HA-70 gene sequence s. Comparison of NTNH/G with other NTNHs reveals that it shows highest homology with NTNH/B consistent with the genealogical affinity shown between BoNT/G and BoNT/B genes.