Mosaic structures of neurotoxins produced from Clostridium botulinum types C and D organisms

We isolated the gene encoding a botulinum neurotoxin (BoNT) of 1285 amino acids with a molecular weight of 147,364 from the toxigenic bacteriophage d-sA of Clostridium botulinum type D strain South African (Dsa). The BoNT of Dsa (BoNT/Dsa) is composed of three regions on the basis of the homology to BoNT types C1 (BoNT/C1) and D (BoNT/D). The N-terminal (Met-1 to Val-522) and the C-terminal regions (Trp-945 to Glu-1285) have high identity to corresponding regions of BoNT/D (96% identity) and BoNT/C1 (74% identity), respectively. The core region (Pro-523 to Lys-944) is common to three toxins (83% to 92% identity). These results suggest that neurotoxins produced from Clostridium botulinum types C and D are composed in a mosaic-like fashion.