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 ~80 kDa and to a lesser extent to an ~ 116 kDa protein(s). Adherence of the neurotoxins to these proteins was enhanced by preincubation of the neurotoxins with GTlb. The ~ 100 kDa heavy chain segment of BTxA adhered to the same proteins. The carboxy terminal half of the heavy chain adhered primarily to the ~80 kDa protein(s) while the amino terminal portion bound most intensely to the ~116 kDa protein(s). The ability of the ~80 and ~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 ~80 and ~116 kDa proteins because tetanus neurotoxin preincubated with GT1b 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.
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