The activation of a G protein–coupled receptor (GPCR) leads to the formation of a ternary complex between agonist, receptor, and G protein that is characterized by high-affinity binding. Allosteric modulators bind to a distinct binding site from the orthosteric agonist and can modulate both the affinity and the efficacy of orthosteric agonists. The influence allosteric modulators have on the high-affinity active state of the GPCR-G protein ternary complex is unknown due to limitations on attempting to characterize this interaction in recombinant whole cell or membrane-based assays. Here, we use the purified M 2 muscarinic acetylcholine receptor reconstituted into nanodiscs to show that, once the agonist-bound high-affinity state is promoted by the G protein, positive allosteric modulators stabilize the ternary complex that, in the presence of nucleotides, leads to an enhanced initial rate of signaling. Our results enhance our understanding of how allosteric modulators influence orthosteric ligand signaling and will aid the design of allosteric therapeutics.

中文翻译：

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GPCR 三元复合物的正变构调节


G 蛋白偶联受体 （GPCR） 的激活导致激动剂、受体和 G 蛋白之间形成三元复合物，其特征是高亲和力结合。变构调节剂与与正构激动剂不同的结合位点结合，并且可以调节正构激动剂的亲和力和功效。变构调节剂对 GPCR-G 蛋白三元复合物的高亲和力活性状态的影响尚不清楚，因为在重组全细胞或基于膜的测定中试图表征这种相互作用的限制。在这里，我们使用重组到纳米盘中的纯化的 M 2 毒蕈碱乙酰胆碱受体来表明，一旦激动剂结合的高亲和力状态被 G 蛋白促进，正变构调节剂就会稳定三元复合物，在核苷酸存在下，导致信号传导的初始速率增强。我们的结果增强了我们对变构调节剂如何影响正构配体信号的理解，并将有助于变构疗法的设计。