Department of Theoretical Physics, Royal Institute of Technology, Stockholm, Sweden.
Biophys J. 2011 Apr 6;100(7):1642-50. doi: 10.1016/j.bpj.2011.02.032.
Cys-loop receptors constitute a superfamily of ion channels gated by ligands such as acetylcholine, serotonin, glycine, and γ-aminobutyric acid. All of these receptors are thought to share structural characteristics, but due to high sequence variation and limited structure availability, our knowledge about allosteric binding sites is still limited. These sites are frequent targets of anesthetic and alcohol molecules, and are of high pharmacological importance. We used molecular simulations to study ethanol binding and equilibrium exchange for the homomeric α1 glycine receptor (GlyRα1), modeled on the structure of the Gloeobacter violaceus pentameric ligand-gated channel. Ethanol has a well-known potentiating effect and can be used in high concentrations. By performing two microsecond-scale simulations of GlyR with/without ethanol, we were able to observe spontaneous binding in cavities and equilibrium ligand exchange. Of interest, it appears that there are ethanol-binding sites both between and within the GlyR transmembrane subunits, with the intersubunit site having the highest occupancy and slowest exchange (∼200 ns). This model site involves several residues that were previously identified via mutations as being crucial for potentiation. Finally, ethanol appears to stabilize the GlyR model built on a presumably open form of the ligand-gated channel. This stabilization could help explain the effects of allosteric ligand binding in Cys-loop receptors.
Cys 环受体构成了一个由配体如乙酰胆碱、血清素、甘氨酸和γ-氨基丁酸等门控的离子通道超家族。所有这些受体都被认为具有结构特征，但由于序列高度变异和结构可用性有限，我们对变构结合位点的了解仍然有限。这些位点是麻醉和酒精分子的常见靶点，具有很高的药理学重要性。我们使用分子模拟研究了同型 α1 甘氨酸受体（GlyRα1）与乙醇的结合和平衡交换，该受体基于 Gloeobacter violaceus 五聚体配体门控通道的结构建模。乙醇具有众所周知的增强作用，并且可以在高浓度下使用。通过对有/无乙醇的 GlyR 进行两次微秒级别的模拟，我们能够观察到空腔中的自发结合和平衡配体交换。有趣的是，似乎在 GlyR 的跨膜亚基之间和内部都存在乙醇结合位点，其中亚基间位点的占据率最高，交换最慢（约 200 ns）。该模型位点涉及几个残基，这些残基先前通过突变被鉴定为对增强作用至关重要。最后，乙醇似乎稳定了基于配体门控通道假定开放形式的 GlyR 模型。这种稳定性可以帮助解释 Cys 环受体中变构配体结合的作用。
