电鳐电器官的蝮蛇突触前神经毒素结合蛋白的一些结合性质

Some Binding Properties of β Agkistrodotoxin binding Protein in Electric Organ of Torpedo

电鳐（Ｔｏｒｐｅｄｏｃａｌｉｆｏｒｎｉｃａ）的电器官是一种富含突触的组织．将这种电器官的粗制膜悬液与同位素１２５Ｉ标记的β－蝮蛇神经毒素进行结合实验，结果表明这种电器官中存在相对含量较高的毒素结合位点，Ｂｍａｘ为１１５０ｆｍｏｌ／ｍｇ，ＫＤ为２．８×１０－８ｍｏｌ／Ｌ．响尾蛇神经毒素和β－银环蛇神经毒素对其结合作用的抑制实验显示，前者与β－蝮蛇神经毒素有共同的结合位点，后者的作用位点则不同．

The electric organ of electric ray( Torpedo californica )is a tissue rich in synapses.The binding experiments of crude membrane preparations of the electric organ with 125 I labelled β agkistrodotoxin were performed.The results indicated that β agkistrodotoxin binding sites existed in this tissue with a density of 1 150 fmol/mg protein,much higher than that of rat brain.The equilibrial dissociation constant K D was 2 8×10 -8 mol/L.And IC 50 of unlabelled β agkistrodotoxin was 5 6×10 -8 mol/L, K i=3 1×10 -8 mol/L.The inhibition experiments of 125 I β agkistrodotoxin binding by crotoxin and β bungarotoxin showed that crotoxin shared a binding site with β agkistrodotoxin,but there was no common binding site for β bungarotoxin and β agkistrodotoxin.It could be inferred that β agkistrodotoxin binding protein,which was different from β bundarotoxin binding protein,was a novel functional protein involved in presynaptic neurotransmitter release mechanism.