Adherence of botulinum and tetanus neurotoxins to synaptosomal proteins

The ability of 125I-labeled botulinum type A and tetanus neurotoxins to adhere to blots of synaptosomal proteins separated by SDS-polyacrylamide gel electrophoresis was studied. Both neurotoxins appeared to adhere preferentially to an approximately 80 kDa and to a lesser extent to an approximately 116 kDa protein(s). Adherence of the neurotoxins to these proteins was enhanced by preincubation of the neurotoxins with GT 1b. The approximately 100 kDa heavy chain segment of BTxA adhered to the same proteins. The carboxy terminal half of the heavy chain adhered primarily to the approximately 80 kDa protein(s) while the amino terminal portion bound most intensely to the approximately 116 kDa protein(s). The ability of the approximately 80 and approximately 116 kDa proteins to stain positively with the periodic acid-Schiff reagent and to bind 125I-labeled wheat germ lectin suggests that they are glycosylated. Both neurotoxins appear to adhere to the same approximately 80 and approximately 116 kDa proteins because tetanus neurotoxin preincubated with GT 1b was able to reduce binding of radiolabeled botulinum type A neurotoxin to both proteins. Neither neurotoxin adhered to blots of proteins from liver, spleen, or kidney, suggesting that the proteins adhered to are neural components.