School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore.
Structural Bioinformatics and Computational Biochemistry, Department of Biochemistry, University of Oxford, Oxford, UK.
Nat Commun. 2024 Apr 5;15(1):2967. doi: 10.1038/s41467-024-47370-w.
GLIC, a proton-activated prokaryotic ligand-gated ion channel, served as a model system for understanding the eukaryotic counterparts due to their structural and functional similarities. Despite extensive studies conducted on GLIC, the molecular mechanism of channel gating in the lipid environment requires further investigation. Here, we present the cryo-EM structures of nanodisc-reconstituted GLIC at neutral and acidic pH in the resolution range of 2.6 - 3.4 Å. In our apo state at pH 7.5, the extracellular domain (ECD) displays conformational variations compared to the existing apo structures. At pH 4.0, three distinct conformational states (C1, C2 and O states) are identified. The protonated structures exhibit a compacted and counter-clockwise rotated ECD compared with our apo state. A gradual widening of the pore in the TMD is observed upon reducing the pH, with the widest pore in O state, accompanied by several layers of water pentagons. The pore radius and molecular dynamics (MD) simulations suggest that the O state represents an open conductive state. We also observe state-dependent interactions between several lipids and proteins that may be involved in the regulation of channel gating. Our results provide comprehensive insights into the importance of lipids impact on gating.
GLIC 是一种质子激活的原核配体门控离子通道，由于其结构和功能上的相似性，它被用作研究真核对应物的模型系统。尽管已经对 GLIC 进行了广泛的研究，但在脂质环境中通道门控的分子机制仍需要进一步研究。在这里，我们展示了中性和酸性 pH 下纳米盘重建的 GLIC 的冷冻电镜结构，分辨率范围为 2.6-3.4Å。在我们的 pH7.5 时的apo 状态下，与现有的 apo 结构相比，细胞外结构域 (ECD) 显示出构象变化。在 pH4.0 时，确定了三种不同的构象状态 (C1、C2 和 O 状态)。与我们的 apo 状态相比，质子化结构显示出紧凑的、逆时针旋转的 ECD。在降低 pH 时，TMD 中的孔逐渐变宽，在 O 状态下最宽，伴随着几层水五边形。孔径和分子动力学 (MD) 模拟表明，O 状态代表一个开放的导电状态。我们还观察到几个脂质和蛋白质之间的状态依赖性相互作用，这些相互作用可能参与通道门控的调节。我们的结果提供了对脂质对门控影响的重要性的全面了解。
