Batebi Hossein, Pérez-Hernández Guillermo, Rahman Sabrina N, Lan Baoliang, Kamprad Antje, Shi Mingyu, Speck David, Tiemann Johanna K S, Guixà-González Ramon, Reinhardt Franziska, Stadler Peter F, Papasergi-Scott Makaía M, Skiniotis Georgios, Scheerer Patrick, Kobilka Brian K, Mathiesen Jesper M, Liu Xiangyu, Hildebrand Peter W
Universität Leipzig, Medizinische Fakultät, Institut für Medizinische Physik und Biophysik, Leipzig, Germany.
Freie Universität Berlin, Fachbereich Physik, Berlin, Germany.
Nat Struct Mol Biol. 2024 Nov;31(11):1692-1701. doi: 10.1038/s41594-024-01334-2. Epub 2024 Jun 12.
G-protein-coupled receptors (GPCRs) activate heterotrimeric G proteins by promoting guanine nucleotide exchange. Here, we investigate the coupling of G proteins with GPCRs and describe the events that ultimately lead to the ejection of GDP from its binding pocket in the Gα subunit, the rate-limiting step during G-protein activation. Using molecular dynamics simulations, we investigate the temporal progression of structural rearrangements of GDP-bound G protein (G·GDP; hereafter G) upon coupling to the β-adrenergic receptor (βAR) in atomic detail. The binding of G to the βAR is followed by long-range allosteric effects that significantly reduce the energy needed for GDP release: the opening of α1-αF helices, the displacement of the αG helix and the opening of the α-helical domain. Signal propagation to the G occurs through an extended receptor interface, including a lysine-rich motif at the intracellular end of a kinked transmembrane helix 6, which was confirmed by site-directed mutagenesis and functional assays. From this βAR-G intermediate, G undergoes an in-plane rotation along the receptor axis to approach the βAR-G state. The simulations shed light on how the structural elements at the receptor-G-protein interface may interact to transmit the signal over 30 Å to the nucleotide-binding site. Our analysis extends the current limited view of nucleotide-free snapshots to include additional states and structural features responsible for signaling and G-protein coupling specificity.
G蛋白偶联受体（GPCRs）通过促进鸟嘌呤核苷酸交换来激活异源三聚体G蛋白。在此，我们研究G蛋白与GPCRs的偶联，并描述最终导致GDP从其在Gα亚基结合口袋中排出的事件，这是G蛋白激活过程中的限速步骤。我们使用分子动力学模拟，从原子层面详细研究了结合GDP的G蛋白（G·GDP；以下简称G）与β-肾上腺素能受体（βAR）偶联后结构重排的时间进程。G与βAR结合后会产生远程变构效应，显著降低GDP释放所需的能量：α1-αF螺旋的打开、αG螺旋的位移以及α-螺旋结构域的打开。信号通过一个扩展的受体界面传递到G，该界面包括一个位于弯曲跨膜螺旋6细胞内末端的富含赖氨酸的基序，这一点通过定点诱变和功能测定得到了证实。从这个βAR-G中间体开始，G沿着受体轴进行平面内旋转，以接近βAR-G状态。这些模拟揭示了受体-G蛋白界面处的结构元件如何相互作用，将信号传递超过30埃至核苷酸结合位点。我们的分析扩展了目前对无核苷酸快照的有限认识，纳入了负责信号传导和G蛋白偶联特异性的其他状态和结构特征。
