Harel M, Schalk I, Ehret-Sabatier L, Bouet F, Goeldner M, Hirth C, Axelsen P H, Silman I, Sussman J L
Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel.
Proc Natl Acad Sci U S A. 1993 Oct 1;90(19):9031-5. doi: 10.1073/pnas.90.19.9031.
Binding sites of Torpedo acetylcholinesterase (EC 3.1.1.7) for quaternary ligands were investigated by x-ray crystallography and photoaffinity labeling. Crystal structures of complexes with ligands were determined at 2.8-A resolution. In a complex with edrophonium, and quaternary nitrogen of the ligand interacts with the indole of Trp-84, and its m-hydroxyl displays bifurcated hydrogen bonding to two members of the catalytic triad, Ser-200 and His-440. In a complex with tacrine, the acridine is stacked against the indole of Trp-84. The bisquaternary ligand decamethonium is oriented along the narrow gorge leading to the active site; one quaternary group is apposed to the indole of Trp-84 and the other to that of Trp-279, near the top of the gorge. The only major conformational difference between the three complexes is in the orientation of the phenyl ring of Phe-330. In the decamethonium complex it lies parallel to the surface of the gorge; in the other two complexes it is positioned to make contact with the bound ligand. This close interaction was confirmed by photoaffinity labelling by the photosensitive probe 3H-labeled p-(N,N-dimethylamino)benzenediazonium fluoroborate, which labeled, predominantly, Phe-330 within the active site. Labeling of Trp-279 was also observed. One mole of label is incorporated per mole of AcChoEase inactivated, indicating that labeling of Trp-279 and that of Phe-330 are mutually exclusive. The structural and chemical data, together, show the important role of aromatic groups as binding sites for quaternary ligands, and they provide complementary evidence assigning Trp-84 and Phe-330 to the "anionic" subsite of the active site and Trp-279 to the "peripheral" anionic site.
通过X射线晶体学和光亲和标记法研究了电鳐乙酰胆碱酯酶（EC 3.1.1.7）与季铵配体的结合位点。测定了与配体形成的复合物的晶体结构，分辨率为2.8埃。在与依酚氯铵形成的复合物中，配体的季铵氮与Trp-84的吲哚相互作用，其间位羟基与催化三联体的两个成员Ser-200和His-440形成分叉氢键。在与他克林形成的复合物中，吖啶堆积在Trp-84的吲哚上。双季铵配体十烃季铵沿着通向活性位点的狭窄峡谷排列；一个季铵基团与Trp-84的吲哚相对，另一个与峡谷顶部附近的Trp-279的吲哚相对。这三种复合物之间唯一主要的构象差异在于Phe-330苯环的取向。在十烃季铵复合物中，它与峡谷表面平行；在另外两种复合物中，它的位置使其与结合的配体接触。通过光敏探针3H标记的对（N，N-二甲基氨基）苯重氮氟硼酸盐进行的光亲和标记证实了这种紧密相互作用，该探针主要标记活性位点内的Phe-330。还观察到Trp-279的标记。每摩尔失活的乙酰胆碱酯酶掺入1摩尔标记，这表明Trp-279和Phe-330的标记是相互排斥的。结构和化学数据共同表明芳香基团作为季铵配体结合位点的重要作用，并且它们提供了互补证据，将Trp-8到活性位点的“阴离子”亚位点，将Trp-279到“外周”阴离子位点。 4和Phe-330分配
原文最后一句“assigning Trp-84 and Phe-330 to the "anionic" subsite of the active site and Trp-279 to the "peripheral" anionic site.”翻译中“Trp-8到活性位点的‘阴离子’亚位点”可能有误，推测原文是“Trp-84”，你可根据实际情况进行调整。
