Dynamics of the Ligand Binding Domain Layer during AMPA Receptor Activation
Dynamics of the Ligand Binding Domain Layer during AMPA Receptor Activation
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DOI：
10.1016/j.bpj.2015.12.033
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发表时间：
2016-02-23
影响因子：
3.4
通讯作者：
Plested, Andrew J. R.
中科院分区：
文献类型：
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作者：
Baranovic, Jelena;Chebli, Miriam;Plested, Andrew J. R.
嗜电性谷氨酸受体是突触后四聚体配体门控通道，其活性介导快速兴奋传递。谷氨酸与贝壳状配体结合域（lbd）的结合触发了完整离子通道的打开，但这四种lbd如何协调受体的激活尚不清楚。在这里，我们展示了一个高分辨率的x射线晶体结构，显示了两个完全结合谷氨酸的四聚体LBD排列。利用一系列工程金属离子诱捕突变体，我们表明，在全长受体激活过程中，两个组装体中更紧密的排列对应于一个填充的排列。突变体的状态依赖交联发现，当四聚体完全或部分与谷氨酸结合时，典型活性LBD二聚体之间形成锌桥。这些桥也稳定了静息状态，与最近发表的全长载脂蛋白结构一致。我们的研究结果为谷氨酸受体的激活机制和LBD层可以采样的复杂构象空间提供了新的思路。
Ionotropic glutamate receptors are postsynaptic tetrameric ligand-gated channels whose activity mediates fast excitatory transmission. Glutamate binding to clamshell-shaped ligand binding domains (LBDs) triggers opening of the integral ion channel, but how the four LBDs orchestrate receptor activation is unknown. Here, we present a high-resolution x-ray crystal structure displaying two tetrameric LBD arrangements fully bound to glutamate. Using a series of engineered metal ion trapping mutants, we showed that the more compact of the two assemblies corresponds to an arrangement populated during activation of full-length receptors. State-dependent cross-linking of the mutants identified zinc bridges between the canonical active LBD dimers that formed when the tetramer was either fully or partially bound by glutamate. These bridges also stabilized the resting state, consistent with the recently published full-length apo structure. Our results provide insight into the activation mechanism of glutamate receptors and the complex conformational space that the LBD layer can sample.