Catterall W A
J Biol Chem. 1976 Sep 25;251(18):5528-36.
Venom of the scorpion Leiurus quinquestriatus acts cooperatively with the alkaloids veratridine, aconitine, and batrachotoxin in activating the action potential Na+ ionophore. A small (Mr = 6700), basic (pI approximately 9.8), toxic polypeptide purified approximately 80-fold from this venom by ion exchange chromatography appears homogeneous by gel electrophoresis and isoelectric focusing and, like whole venom, acts cooperatively with the alkaloids veratridine, aconitine, and batrachotoxin to activate the action potential Na+ ionophore. The action of the scorpion toxin is slowly reversible. Concentration-response curves suggest interaction with a single class of sites with KD - 1.3 to 2.4 nM. The scorpion toxin is a poor activator of the Na+ ionophore when tested alone. However, treatment of cells sequentially with scorpion toxin followed by veratridine activates as well as treatment with both simultaneously suggesting that scorpion toxin binds in the absence of veratridine but does not activate the Na+ ionophore unless veratridine is present. In contrast, scorpion toxin causes 3- to 20-fold decreases in apparent KD for aconitine, veratridine, and batrachotoxin. The effect of the toxin is inhibited competitively by divalent cations and noncompetitively by tetrodotoxin (KI - 4 nM).
以色列金蝎的毒液与藜芦碱、乌头碱和箭毒蛙毒素等生物碱协同作用，激活动作电位的钠离子载体。一种小分子量（Mr = 6700）、碱性（pI约为9.8）的有毒多肽，通过离子交换色谱从这种毒液中纯化了约80倍，经凝胶电泳和等电聚焦显示为均一状态，并且与全毒液一样，能与藜芦碱、乌头碱和箭毒蛙毒素协同作用，激活动作电位的钠离子载体。蝎毒素的作用是缓慢可逆的。浓度 - 反应曲线表明其与一类单一的位点相互作用，KD为1.3至2.4 nM。单独测试时，蝎毒素是钠离子载体的较弱激活剂。然而，先用蝎毒素处理细胞，然后再用藜芦碱处理，其激活效果与同时使用两者相同，这表明蝎毒素在没有藜芦碱的情况下也能结合，但除非有藜芦碱存在，否则不会激活钠离子载体。相比之下，蝎毒素会使乌头碱、藜芦碱和箭毒蛙毒素的表观KD降低3至20倍。毒素的作用受到二价阳离子的竞争性抑制和河豚毒素的非竞争性抑制（KI - 4 nM）。
