Nicotinic acetylcholine receptor contains multiple binding sites: evidence from binding of alpha-dendrotoxin.
Nicotinic acetylcholine receptor contains multiple binding sites: evidence from binding of alpha-dendrotoxin.
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烟碱乙酰胆碱受体包含多个结合位点：来自α-树突毒素结合的证据。
DOI：
10.1073/pnas.83.17.6646
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发表时间：
1986
影响因子：
11.1
通讯作者：
Raftery,MA
中科院分区：
文献类型：
--
作者：
Conti-Tronconi,BM;Raftery,MA
本文研究了绿色树盾蚧（Dendroaspis viridis）毒（α-dendrotoxin）和暹罗眼镜蛇毒（α-cobratoxin）的长α-神经毒素与加利福尼亚电鳐（Torpedo californica）电器官膜结合乙酰胆碱受体（AcChoR）结合的化学计量学。通过对AcChoR-α-神经毒素复合物中存在的所有氨基酸序列进行快速定量气相微测序，确定与一个AcChoR分子结合的毒素分子的数量。该方法允许使用天然毒素的均质（非放射性标记）制剂，以获得神经毒素-受体复合物的摩尔比。α-眼镜蛇毒素的化学计量为2.1 +/- 0.2（n = 4），与公认的观点一致，即α-眼镜蛇毒素与α-银环蛇毒素一样，与AcChoR分子的两个α亚基结合。α-树毒素的化学计量为4.1 +/-0.5（n = 12）;因此，AcChoR分子含有该α-神经毒素的四个结合位点，其中两个被α-眼镜蛇毒素识别。为了支持这一论点，我们还发现，当AcChoR被α-银环蛇毒素饱和时，加入α-树枝毒素显著加速结合的α-银环蛇毒素的解离，表明后一种毒素对另外两个位点的占据影响并降低了前一种毒素对其两个结合位点的亲和力。AcChoR分子是五个高度同源肽的假对称复合物，这一事实表明可能存在多达五个胆碱能配体的结合位点，每个亚基上一个。
We have studied the stoichiometry of the binding of the long alpha-neurotoxins from the venom of Dendroaspis viridis (alpha-dendrotoxin) and Naja naja siamensis (alpha-cobratoxin) to the membrane-bound acetylcholine receptor (AcChoR) from Torpedo californica electric organ. The number of toxin molecules bound to one AcChoR molecule was determined by simultaneous-quantitative gas-phase microsequencing of all the amino acid sequences present in AcChoR-alpha-neurotoxin complexes. This method permits the use of homogeneous (nonradiolabeled) preparations of native toxins to obtain molar ratios of neurotoxin-receptor complexes. The stoichiometry obtained for alpha-cobratoxin was 2.1 +/- 0.2 (n = 4), in agreement with the accepted view that alpha-cobratoxin, like alpha-bungarotoxin, binds to the two alpha subunits, which are constituent polypeptides of the AcChoR molecule. alpha-Dendrotoxin gave a stoichiometry of 4.1 +/- 0.5 (n = 12); therefore, the AcChoR molecule contains four binding sites for this alpha-neurotoxin, two of which are recognized by alpha-cobratoxin. In support of this contention we have also found that when the AcChoR is saturated with alpha-bungarotoxin, addition of alpha-dendrotoxin markedly accelerates the dissociation of the bound alpha-bungarotoxin, demonstrating that the occupancy of the additional two sites by the latter toxin influences and decreases the affinity of the former toxin for its two binding sites. The fact that the AcChoR molecule is a pseudosymmetric complex of five highly homologous peptides suggests the possibility that as many as five binding sites for cholinergic ligand could be present, one on each subunit.