A rapid method for the preparation of (125I)alpha-bungarotoxin

Electrofocusing followed by chromatography on Sephadex G-50 proved to be a fast method for the purification of the neurotoxin, α-bungarotoxin (α-BGT) from the venom of the krait (Bungarus multicinctus). The purity of the isolated α-BGT was checked by electrofocusing and ion-exchange chromatography. Blockade of the binding of ³H]ACh to the acetylcholine receptor in a membrane preparation of Torpedo electroplax was a convenient biochemical assay to identify the α-neurotoxin polypeptide. Iodination, accomplished by lactoperoxidase attached to Sepharose 4B, was simple and rapid, with a 60% recovery of ¹²⁵I]α-BGT. Biological activity of the α-BGT was determined by its toxicity to mice as well as by autoradiography of ¹²⁵I]α-BGT which proved its localization in the endplates of the mouse diaphragms.