Department of Cell Biology, Microbiology and Molecular Biology, University of South Florida, Tampa, FL, 33620, USA.
Theoretical Biology and Biophysics, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
Nat Commun. 2023 Mar 10;14(1):1325. doi: 10.1038/s41467-023-36971-6.
Understanding the roles of intermediate states in signaling is pivotal to unraveling the activation processes of G protein-coupled receptors (GPCRs). However, the field is still struggling to define these conformational states with sufficient resolution to study their individual functions. Here, we demonstrate the feasibility of enriching the populations of discrete states via conformation-biased mutants. These mutants adopt distinct distributions among five states that lie along the activation pathway of adenosine A receptor (AR), a class A GPCR. Our study reveals a structurally conserved cation-π lock between transmembrane helix VI (TM6) and Helix8 that regulates cytoplasmic cavity opening as a "gatekeeper" for G protein penetration. A GPCR activation process based on the well-discerned conformational states is thus proposed, allosterically micro-modulated by the cation-π lock and a previously well-defined ionic interaction between TM3 and TM6. Intermediate-state-trapped mutants will also provide useful information in relation to receptor-G protein signal transduction.
理解中间状态在信号转导中的作用对于揭示 G 蛋白偶联受体 (GPCR) 的激活过程至关重要。然而，该领域仍在努力定义这些构象状态，以获得足够的分辨率来研究它们的单独功能。在这里，我们证明了通过构象偏向突变体来富集离散状态群体的可行性。这些突变体在沿着腺苷 A 受体 (AR) 激活途径的五个状态之间呈现出不同的分布，AR 是 A 类 GPCR。我们的研究揭示了跨膜螺旋 VI (TM6) 和螺旋 8 之间结构保守的阳离子-π 锁定，作为 G 蛋白穿透的“守门员”，调节细胞质腔的打开。因此，提出了一种基于区分明显构象状态的 GPCR 激活过程，该过程由阳离子-π 锁定和之前定义明确的 TM3 和 TM6 之间的离子相互作用进行变构微调节。中间状态捕获突变体也将为受体- G 蛋白信号转导提供有用的信息。
