M1毒蕈碱乙酰胆碱受体同源建模模板的选取及验证

Evaluation and Validation of Homology Models of M1 Muscarinic Acetylcholine Receptor

目的:探讨不同同源模板所获得M1毒蕈碱乙酰胆碱受体模型的合理性及可靠性。方法:以牛视紫红素受体、人源β2-肾上腺素受体、M2胆碱受体和M3胆碱受体为模板,分别对M1胆碱受体进行同源建模;采用分子对接获得各M1胆碱受体同源模板与配体的互作模式,并与已报道的M胆碱受体晶体结构进行静态比对,得到最佳M1胆碱受体同源模板;采用分子动力学模拟分析配体与关键残基距离的变化,对M1胆碱受体同源模板进行动态验证。结果:M2胆碱受体与M1胆碱受体的序列相似度较高,为67.9%;以Inactive M2胆碱受体为模板构建的M1胆碱受体(M1R_(inactive-M2R))与其他晶体结构间RMSD值的均值最低,为1.39;M1R_(inactive-M2R)别构位点K392及E397残基侧链与结合口袋距离更近,与配体结合构象更匹配;分子对接结果显示,双位点别构激动剂VU0184670与M1R_(inactive-M2R)别构结合位点Y85、Y381的距离分别为4.8、6.8,优于其他模型;分子动力学模拟后,配体与Q177残基的距离由7.4降至2.9,提示配体VU0184670向Q177方向偏转,与文献结果一致。结论:以Inactive M2受体结构为模板构建的M1胆碱受体模型最为合理,更接近M1胆碱受体的晶体结构。本研究为M1胆碱受体药物开发提供重要工具,为其他GPCRs受体同源建模提供创新范式。

Objective： To evaluate the reasonability and reliability of M 1 muscarinic acetylcholine receptor （mAChR） constructed fi＇om different GPCR models. Methods： M1 mAChRs complexes were obtained by homology modeling from bovine rhodopsin, human β 2-adrenergic receptors, human M2 and M3 mAChRs. The receptor-ligand interactions were obtained by docking, and were compared with the crystal structure of M 1 mAChR in static state. The variety of distances between ligand and crucial residues of M 1 mAChR were evaluated by molecular dynamic simulation to validate the optimum model of M1 mAChR in dynamic state. Results： M2 mAChR possessed highest sequence similarities with M1 mAChR （67.9%）. The mean of RMSDs between the M1 mAChR constructed by Inactive M2 （M1Pimactive-M2R） and other crystal structures was smallest （1.39 A）. The allosteric sites （K392 and E397） of M1Rimactive-M2R were closer to the binding pockets, which were corresponded with the ligand binding conformation. Docking results showed that the distances between bitopic allosteric agonist （VU0184670） and allosteric sites 0（85 and Y381） of M1Rinactive-M2R were 4.8 A and 6.8 A respectively, more reasonable than other M1 mAChR models. The distance between ligand and residue of Q177 was decreased from 7.4 A to 2.9 A after dynamic simulation, indicating the rotation of VU0184670 towards Q 177, which was corresponded to previously reported results. Conclusions： Our results have proved that the M1 mAChR constructed by Inactive M2 mAChR （M1Rimactive-M2R） exhibited high structural similarity with crystal structure of M1 mAChR and was reasonable and reliable in both static and dynamic states. Our study provides important strategies for the development of M 1 mAChR drugs, and also novel paradigms for the exploration of other GPCRs.