Direct structural localization of two toxin-recognition sites on an ACh receptor protein-猫眼课题宝

ACh 受体蛋白上两个毒素识别位点的直接结构定位

DOI：

发表时间：

1982

期刊：

Nature

影响因子：

64.8

通讯作者：

中科院分区：

综合性期刊1区

文献类型：

作者：

H. Zingsheim;F. Barrantes;J. Frank;W. Hänicke;D. Neugebauer

研究最活跃的化学感受器之一是神经肌肉接头和电细胞的突触后膜中的乙酰胆碱受体（AChR）。电鳐的AChR是一种膜蛋白，每个分子包含5条多肽链1，2：两条分子量（Mr）为40，000的α链，以及三条Mr为50，000（β）、60，000（γ）和65，000（δ）的同源链。似乎只有α-峰携带激动剂和拮抗剂的特异性识别位点2。由于蛇α-神经毒素似乎高度特异性地和准不可逆地结合到这些位点上，我们使用天然α-银环蛇毒素（α-BTX，Mr 8，000;参考文献3）作为标记物，进行了结构分析以定位α-亚基。我们在这里报告了通过电子显微镜和单粒子图像平均4在20 μ m分辨率下获得的结果，这些结果揭示了AChR结构内两个明确的区域5，6，其中质量在α-BTX结合时显着增加。其中一个区域（α 1）与δ亚基所在的区域相邻;第二个区域（α 2）在分子的直径方向上，与δ亚基和（α 1）相距约50 nm。通过直接结构分析揭示的形貌可以解释先前最近邻交联研究的结果2，7。

One of the most actively studied chemoreceptors is the acetylcholine receptor (AChR) in the postsynaptic membranes of neuromuscular junctions and electrocytes. The AChR from Torpedo is a membrane protein, each molecule comprising five polypeptide chains1,2: two α-chains of molecular weight (Mr) 40,000, and three homologous chains of Mr 50,000 (β), 60,000 (γ) and 65,000 (δ). Only the α-summits seem to carry the specific recognition sites for agonists and antagonists2. As snake α-neurotoxins seem to bind highly specifically and quasi-irreversibly to these sites we performed a structural analysis to localize the α-subunits, using as marker native α-bungarotoxin (α-BTX, Mr 8,000; ref. 3). We report here the results obtained at 20 Å resolution by electron microscopy and single-particle image averaging4, which reveal two well-defined regions within the AChR structure5,6 where the mass increases significantly on binding of α-BTX. One of these (α1) is adjacent to the region where the δ-subunit has been located6; the second region (α2) is diametrically across the molecule, ∼50 Å away from the δ-subunit and also from (α1). The topography revealed by direct structural analysis can explain the results of previous nearest-neighbour cross-linking studies2,7.

Crystalline arrays of membrane-bound acetylcholine receptor.