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A binding characteristic of neurotoxins from bungarus fasciatus venom to acetylcholine receptor

Hsu Ke, Chen Lijun, Jiang Mindshi

Shanghai Institute of Physiology, Academia Sinica. Shanghai, China

Abstract

The crude venom of Bungarus fasciatus was fractionated by ion-exchange chromatography on a CM-Sephadex C-50 column into 11 fractions. Two neurotoxic fractions obtained were further purified on CM-Cellulose C-32 and Sephadex G-50 columns. They were basic proteins and named as neurotoxin I (TI) and neurotoxin II (TH). Both of them lacked phospholipase A activity. Test of neuromuscular transmission on the chick biventer cervicis nerve-muscle preparation showed that both TI and TII belonged to the postsynaptic type. The mouse minimal lethal dose (i. p.) of TI and TII was about 200 r and 250 r per kg body weight respectively. The competitive inhibitory effects of the two neurotoxins on the binding of ~(125)I-bungarotoxin or ~(125)I-cobrotoxin to AChR were studied. After preincubation of the narcine AChR (Triton X-100 solubilized extract or the preparation further purified by affinity chromatography) with various amounts of TI or TII (for 10 minutes or 1 hour), ~(125)I-bungarotoxin or ~(125)I-cobrotoxin were added and the residual binding of the latter to AChR were determined. The results showed that even with excessive amounts of TI or TII, the total binding of u-bungarotoxin or cobrotoxin to AChR was only competitively blocked about 2/3. The possibility of two kinds of AChR existing was discussed.

Key words: Bungarus fasciatus neurotoxin;Alpha-bungarotoxin;Cobrotoxin;Acety1choline receptor;Cobrotosin-4 B affinity chromatography

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Citing This Article：

Hsu Ke, Chen Lijun, Jiang Mindshi. A binding characteristic of neurotoxins from bungarus fasciatus venom to acetylcholine receptor. Acta Physiol Sin 1985; 37 (2): (in Chinese with English abstract).