Interaction with chick myotube cholinergic receptors of an alpha-neurotoxin isolated from venom of the banded krait (Bungarus fasciatus)

• Published in: Toxicon (Oxford) Vol. 24; no. 7; p. 713
• Main Authors: Jiang, M S, Häggblad, J, Heilbronn, E
• Format: Journal Article
• Language: English
• Published: England 1986
• Subjects: alpha7 Nicotinic Acetylcholine Receptor; Animals; Binding, Competitive; Bungarotoxins - metabolism; Carbachol - antagonists & inhibitors; Chick Embryo; Culture Techniques; Elapid Venoms - analysis; Epitopes; Molecular Weight; Muscles - metabolism; Neurotoxins - isolation & purification; Neurotoxins - metabolism; Neurotoxins - pharmacology; Receptors, Cholinergic - metabolism; Receptors, Nicotinic
• ISSN: 0041-0101
• DOI: 10.1016/0041-0101(86)90034-6

A postsynaptic acting short chain alpha-toxin, B.f. III, was isolated from venom of the banded krait (Bungarus fasciatus) using ion-exchange chromatography. The toxin, a basic protein (pI = 10) has an apparent molecular weight of 6,500 as determined by SDS-polyacrylamide gel electrophoresis. It shares immunological determinants with alpha-bungarotoxin, as it cross-reacted with antibodies raised in rabbits against alpha-bungarotoxin. B.f. III inhibits binding of 125I-alpha-bungarotoxin to cultured chick myotubes with an IC50 of 3 X 10(-10) M. The rate of association with chick myotube nAChR was 3 times faster than that of alpha-bungarotoxin, and binding was slowly reversible. The toxin is a less potent antagonist than alpha-bungarotoxin; in ion flux experiments, measuring influx of 86Rb in chick myotubes, B.f. III inhibited carbachol-induced influx of 86Rb (IC50 = 5 X 10(-9) M) at concentrations higher than those needed for alpha-bungarotoxin (IC50 = 6 X 10(-10) M).