Department of Biochemistry, University of Cambridge, 80 Tennis Court Road, Cambridge, CB2 1GA, UK.
Protein Sciences, CBT, Novartis Institutes for BioMedical Research (NIBR), CH-4002, Basel, Switzerland.
Nat Commun. 2017 Nov 27;8(1):1795. doi: 10.1038/s41467-017-02008-y.
A complex conformational energy landscape determines G-protein-coupled receptor (GPCR) signalling via intracellular binding partners (IBPs), e.g., G and β-arrestin. Using C methyl methionine NMR for the β-adrenergic receptor, we identify ligand efficacy-dependent equilibria between an inactive and pre-active state and, in complex with G-mimetic nanobody, between more and less active ternary complexes. Formation of a basal activity complex through ligand-free nanobody-receptor interaction reveals structural differences on the cytoplasmic receptor side compared to the full agonist-bound nanobody-coupled form, suggesting that ligand-induced variations in G-protein interaction underpin partial agonism. Significant differences in receptor dynamics are observed ranging from rigid nanobody-coupled states to extensive μs-to-ms timescale dynamics when bound to a full agonist. We suggest that the mobility of the full agonist-bound form primes the GPCR to couple to IBPs. On formation of the ternary complex, ligand efficacy determines the quality of the interaction between the rigidified receptor and an IBP and consequently the signalling level.
一个复杂的构象能量景观通过细胞内结合伙伴（IBP），例如 G 蛋白和β-arrestin，决定 G 蛋白偶联受体（GPCR）信号转导。我们使用 C 甲基甲硫氨酸 NMR 对β-肾上腺素受体进行研究，确定了配体效力依赖性的无活性和前活性状态之间的平衡，以及与 G 模拟纳米体结合时，更活跃和不那么活跃的三元复合物之间的平衡。通过无配体的纳米体-受体相互作用形成基础活性复合物，揭示了与完全激动剂结合的纳米体偶联形式相比，细胞质受体侧的结构差异，表明配体诱导的 G 蛋白相互作用变化是部分激动作用的基础。当与完全激动剂结合时，观察到受体动力学的显著差异，范围从刚性纳米体结合状态到广泛的微秒至毫秒时间尺度动力学。我们认为，完全激动剂结合形式的流动性使 GPCR 能够与 IBP 偶联。在三元复合物形成时，配体效力决定了刚性化受体与 IBP 之间相互作用的质量，进而决定了信号转导水平。
