Isolation and pharmacological characterization of a new α-neurotoxin (α-AgTx) from venom of the viper Agkistrodon halys (Pallas)

A hitherto unknown alpha-neurotoxin, alpha-agkistrodotoxin, was isolated from the venom of the pit viper Agkistrodon halys (Pallas). It's molecular weight was approx. 8000 +/- 80 (SDS-polyacrylamide electrophoresis). The toxin crossreacted with antiserum directed against alpha-bungarotoxin and inhibited binding of 125I-alpha-bungarotoxin to the nicotinic acetylcholine receptor of cultured myotubes (IC50 = 2 X 10(-9) M). The association and dissociation rates were 4.85 X 10(5) per mole per min and 3.55 X 10(-4) per min, respectively, giving a Kd of 7.3 X 10(-10) M. The toxin also inhibited carbachol-induced influx of cations through the nAChR (IC50 = 6 X 10(-8) M).