Inhibition of norepinephrine secretion from digitonin permeabilized PC12 cells by botulinum type D toxin.

Toxigenic strains of Clostridium botulinum produced seven immunological distinct neurotoxins, type A-G. Neurotoxins are 150-kDa proteins, synthesized as single chain molecules and nicked to the dichain form by endogenous protease(s) in the bacterial culture. Dichain form consists of a heavy chain (approx. 100 kDa) and a light chain (approx. 50 kDa) held together by at least one disulfide bond and noncovalent bonds.