MOSAIC STRUCTURES OF NEUROTOXINS PRODUCED FROM CLOSTRIDIUM-BOTULINUM TYPE-C AND TYPE-D ORGANISMS

We isolated the gene encoding a botulinum neurotoxin (BoNT) of 1285 am ino acids with a molecular weight of 147 364 from the toxigenic bacter iophage d-sA of Clostridium botulinum type D strain South African (Dsa ). The BoNT of Dsa (BoNT/Dsa) is composed of three regions on the basi s of the homology to BoNT types Cl (BoNT/Cl) and D (BoNT/D). The N-ter minal (Met-1 to Val-522) and the C-terminal regions (Trp-945 to Glu-12 85) have high identity to corresponding regions of BoNT/D (96% identit y) and BoNT/Cl (74% identity), respectively. The core region (Pro-523 to Lys-944) is common to three toxins (83% to 92% identity). These res ults suggest that neurotoxins produced from Clostridium botulinum type s C and D an composed in a mosaic-like fashion.