Laboratori de Medicina Computacional, Unitat de Bioestadística , Facultat de Medicina, Universitat Autònoma de Barcelona , 08193 Bellaterra , Spain.
Department of Pharmacy , University of Patras , 26500 Patras , Greece.
J Chem Inf Model. 2018 May 29;58(5):1074-1082. doi: 10.1021/acs.jcim.8b00108. Epub 2018 May 2.
The muscarinic M acetylcholine receptor, one of the few G-protein coupled receptors that has not only been crystallized in both active and inactive conformations but also in the presence of a positive allosteric modulator, is an interesting system to study the molecular mechanisms of GPCR activation and ligand allosterism. Here, we have employed molecular dynamics (MD) simulations (adding to 14 μs in total) to study conformational changes triggered by the inverse agonist R-(-)-3-quinuclidinyl-benzilate (QNB) in the structure of the active M receptor (PBD ID 4MQS ) after replacement of the agonist iperoxo by the inverse agonist QNB. This permitted us to identify the sequence of events in the deactivation mechanism of the M acetylcholine receptor, which results first in the rearrangement of the transmission switch, the subsequent opening of the extracellular portion of the receptor and finally, the closure of the intracellular part. We also evaluate the effect of the positive allosteric modulator LY2119620 when bound simultaneously with the orthosteric agonist iperoxo and find that it restricts the conformation of Trp422 in a position that modulates the orientation of the Tyr426 at the orthosteric-binding pocket.
毒蕈碱型 M 乙酰胆碱受体是少数已被结晶为活性和非活性构象的 G 蛋白偶联受体之一，同时也被结晶为与正变构调节剂结合的状态，是研究 GPCR 激活和配体变构机制的有趣体系。在这里，我们采用分子动力学（MD）模拟（总计增加 14 μs），研究了在激动剂异丙氧肟取代为反向激动剂 QNB 后，活性 M 受体（PBD ID 4MQS）结构中反向激动剂 R-(-)-3-奎宁环基-苯甲酰基（QNB）引发的构象变化。这使我们能够确定 M 乙酰胆碱受体失活机制中的事件顺序，首先是传输开关的重新排列，随后是受体胞外部分的打开，最后是胞内部分的关闭。我们还评估了正变构调节剂 LY2119620 与正位激动剂异丙氧肟同时结合时的影响，发现它限制了 Trp422 的构象，从而调节 Tyr426 在正位结合口袋中的取向。
