Tryptic Peptide Fragments of the Principal Curarimimetic Neurotoxin from the Venom of the Thailand Cobra, Naja Naja Siamensis
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Neurotoxin-3 from the venom of the Thailand Cobra, Naja naja siamensis, was reduced and S-carboxymethylated prior to undergoing digestion by trypsin. The resulting five major tryptic peptide fragments were partially separated chromatographically and their ability to bind to the acetylcholine receptor site (AchR) was examined. Results based on a 30-min. time point seemed to indicate that some of the peptides inhibit the binding of 125 I-α- bungarotoxin to the AchR at concentrations in the range of 10-6 - 10-4 M. One particular peptide, which is thought to contain the majority of important residues making up the "toxic loop," exhibited pronounced inhibition. Results from a kinetic binding study indicated that this peptide possibly exhibits inhibition at a concentration in the range of 3. 46 X 10 -6 - 6 .91 X 10 -6 M.