Jiang M S, Häggblad J, Heilbronn E
Toxicon. 1986;24(7):713-9. 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).
利用离子交换色谱法从银环蛇（Bungarus fasciatus）毒液中分离出一种突触后作用的短链α-毒素B.f. III。该毒素是一种碱性蛋白（等电点=10），通过SDS-聚丙烯酰胺凝胶电泳测定其表观分子量为6500。它与α-银环蛇毒素具有共同的免疫决定簇，因为它能与兔抗α-银环蛇毒素抗体发生交叉反应。B.f. III抑制125I-α-银环蛇毒素与培养的鸡肌管结合，半数抑制浓度（IC50）为3×10^(-10) M。其与鸡肌管烟碱型乙酰胆碱受体（nAChR）的结合速率比α-银环蛇毒素快3倍，且结合缓慢可逆。该毒素作为拮抗剂的效力低于α-银环蛇毒素；在离子通量实验中，通过测量鸡肌管中86Rb的内流，B.f. III在高于α-银环蛇毒素所需浓度（IC50 = 6×10^(-10) M）时抑制卡巴胆碱诱导的86Rb内流（IC50 = 5×10^(-9) M）。
