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Studies on the active region of botulinus toxins : involvement and sequence of a peptide in the region of the single cysteine residue in botulinus toxins types A, B and E Van Alstyne, Diane

Abstract

After establishing that, like types B and E toxins, type A botulinus toxin contains only one residue of cysteine per molecule, chemical modification studies were carried out showing that sulfhydryl-specific reagents like p-chloromercuribenzoate (PCMB) and N-(4-dimethyl-amino-3,5-dinitrophenyl) maleimide (DDPM) cause a marked decrease in toxicity. Types A, B and E toxins were reacted with DDPM and a labelled peptide was obtained from the tryptic digest of each of the toxins. The quantitative amino acid analyses of these three peptides were remarkably similar. Sequence analyses showed that a sequence ala-glu-ser-cys-ser-asp-ser is common to all three DDPS-peptides. Type B botulinus toxin does not enzymatically alter acetylcholine in order to cause flaccid paralysis. It is postulated that the three thiol-containing peptides isolated contain all or part of a postulated active site common to each of types A, B and E botulinus toxins.

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