Department of Biotechnology & Biophysics, Julius-Maximilians-University Würzburg, Würzburg, Germany.
Neurobiology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, UK.
Commun Biol. 2021 Sep 9;4(1):1056. doi: 10.1038/s42003-021-02605-0.
Ionotropic glutamate receptors (iGluRs) mediate signal transmission in the brain and are important drug targets. Structural studies show snapshots of iGluRs, which provide a mechanistic understanding of gating, yet the rapid motions driving the receptor machinery are largely elusive. Here we detect kinetics of conformational change of isolated clamshell-shaped ligand-binding domains (LBDs) from the three major iGluR sub-types, which initiate gating upon binding of agonists. We design fluorescence probes to measure domain motions through nanosecond fluorescence correlation spectroscopy. We observe a broad kinetic spectrum of LBD dynamics that underlie activation of iGluRs. Microsecond clamshell motions slow upon dimerization and freeze upon binding of full and partial agonists. We uncover allosteric coupling within NMDA LBD hetero-dimers, where binding of L-glutamate to the GluN2A LBD stalls clamshell motions of the glycine-binding GluN1 LBD. Our results reveal rapid LBD dynamics across iGluRs and suggest a mechanism of negative allosteric cooperativity in NMDA receptors.
离子型谷氨酸受体（iGluRs）在大脑中介导信号传递，是重要的药物靶点。结构研究显示了 iGluRs 的快照，为门控提供了机械理解，但驱动受体机制的快速运动在很大程度上难以捉摸。在这里，我们检测了来自三种主要 iGluR 亚型的孤立蛤壳状配体结合域（LBD）的构象变化动力学，这些 LBD 在与激动剂结合时会引发门控。我们设计荧光探针通过纳秒荧光相关光谱法测量域运动。我们观察到 LBD 动力学的广泛动力学谱，这是 iGluRs 激活的基础。微秒蛤壳运动在二聚化时减慢，并在完全和部分激动剂结合时冻结。我们揭示了 NMDA LBD 异源二聚体中的变构偶联，其中 L-谷氨酸与 GluN2A LBD 的结合会使甘氨酸结合的 GluN1 LBD 的蛤壳运动停滞。我们的结果揭示了 iGluRs 中的快速 LBD 动力学，并提出了 NMDA 受体中负变构协同作用的机制。
