Department of Chemistry, University of Toronto, UTM, Mississauga, Ontario, Canada.
Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
Nat Struct Mol Biol. 2023 Apr;30(4):502-511. doi: 10.1038/s41594-023-00957-1. Epub 2023 Mar 30.
Heterotrimeric G proteins serve as membrane-associated signaling hubs, in concert with their cognate G-protein-coupled receptors. Fluorine nuclear magnetic resonance spectroscopy was employed to monitor the conformational equilibria of the human stimulatory G-protein α subunit (Gα) alone, in the intact Gαβγ heterotrimer or in complex with membrane-embedded human adenosine A receptor (AR). The results reveal a concerted equilibrium that is strongly affected by nucleotide and interactions with the βγ subunit, the lipid bilayer and AR. The α1 helix of Gα exhibits significant intermediate timescale dynamics. The α4β6 loop and α5 helix undergo membrane/receptor interactions and order-disorder transitions respectively, associated with G-protein activation. The αN helix adopts a key functional state that serves as an allosteric conduit between the βγ subunit and receptor, while a significant fraction of the ensemble remains tethered to the membrane and receptor upon activation.
异三聚体 G 蛋白作为膜相关信号枢纽，与它们的同源 G 蛋白偶联受体协同作用。利用氟核磁共振波谱学监测人刺激性 G 蛋白α 亚基（Gα）单独、在完整的 Gαβγ 三聚体中或与嵌入膜中的人腺苷 A 受体（AR）形成复合物时的构象平衡。结果表明存在协同平衡，该平衡受核苷酸和与βγ 亚基、脂双层和 AR 的相互作用强烈影响。Gα 的α1 螺旋表现出显著的中间时间尺度动力学。α4β6 环和α5 螺旋分别经历膜/受体相互作用和有序-无序转变，与 G 蛋白激活相关。αN 螺旋采用关键功能状态，作为βγ 亚基和受体之间的变构通道，而在激活时，部分复合物仍然与膜和受体结合。
