Glycine receptors (GlyRs) are pentameric, ‘Cys-loop’ receptors that form chloride-permeable channels and mediate fast inhibitory signalling throughout the central nervous system^1,2. In the spinal cord and brainstem, GlyRs regulate locomotion and cause movement disorders when mutated^2,3. However, the stoichiometry of native GlyRs and the mechanism by which they are assembled remain unclear, despite extensive investigation^4,5,6,7,8. Here we report cryo-electron microscopy structures of native GlyRs from pig spinal cord and brainstem, revealing structural insights into heteromeric receptors and their predominant subunit stoichiometry of 4α:1β. Within the heteromeric pentamer, the β(+)–α(−) interface adopts a structure that is distinct from the α(+)–α(−) and α(+)–β(−) interfaces. Furthermore, the β-subunit contains a unique phenylalanine residue that resides within the pore and disrupts the canonical picrotoxin site. These results explain why inclusion of the β-subunit breaks receptor symmetry and alters ion channel pharmacology. We also find incomplete receptor complexes and, by elucidating their structures, reveal the architectures of partially assembled α-trimers and α-tetramers.

甘氨酸受体 (GlyRs) 是五聚体“半胱氨酸环”受体，可形成氯离子可渗透通道并在整个中枢神经系统中介导快速抑制信号^1,2。在脊髓和脑干中，GlyR 调节运动并在突变时引起运动障碍^2,3。然而，尽管进行了广泛的调查，但天然 GlyR 的化学计量及其组装机​​制仍不清楚^4,5,6,7,8. 在这里，我们报告了来自猪脊髓和脑干的天然 GlyR 的冷冻电子显微镜结构，揭示了对异聚受体及其主要亚基 4α:1β 化学计量的结构洞察。在异聚五聚体中，β(+)–α(−) 界面采用不同于 α(+)–α(−) 和 α(+)–β(−) 界面的结构。此外，β-亚基包含一个独特的苯丙氨酸残基，位于孔内并破坏典型的印防己毒素位点。这些结果解释了为什么包含 β-亚基会破坏受体对称性并改变离子通道药理学。我们还发现了不完整的受体复合物，并通过阐明它们的结构，揭示了部分组装的 α-三聚体和 α-四聚体的结构。