ジャーナル: Nature / 年: 2016 タイトル: Structural basis of kainate subtype glutamate receptor desensitization. 著者: Joel R Meyerson / Sagar Chittori / Alan Merk / Prashant Rao / Tae Hee Han / Mihaela Serpe / Mark L Mayer / Sriram Subramaniam / 要旨: Glutamate receptors are ligand-gated tetrameric ion channels that mediate synaptic transmission in the central nervous system. They are instrumental in vertebrate cognition and their dysfunction ...Glutamate receptors are ligand-gated tetrameric ion channels that mediate synaptic transmission in the central nervous system. They are instrumental in vertebrate cognition and their dysfunction underlies diverse diseases. In both the resting and desensitized states of AMPA and kainate receptor subtypes, the ion channels are closed, whereas the ligand-binding domains, which are physically coupled to the channels, adopt markedly different conformations. Without an atomic model for the desensitized state, it is not possible to address a central problem in receptor gating: how the resting and desensitized receptor states both display closed ion channels, although they have major differences in the quaternary structure of the ligand-binding domain. Here, by determining the structure of the kainate receptor GluK2 subtype in its desensitized state by cryo-electron microscopy (cryo-EM) at 3.8 Å resolution, we show that desensitization is characterized by the establishment of a ring-like structure in the ligand-binding domain layer of the receptor. Formation of this 'desensitization ring' is mediated by staggered helix contacts between adjacent subunits, which leads to a pseudo-four-fold symmetric arrangement of the ligand-binding domains, illustrating subtle changes in symmetry that are important for the gating mechanism. Disruption of the desensitization ring is probably the key switch that enables restoration of the receptor to its resting state, thereby completing the gating cycle.
温度: 291 K / 手法: 蒸気拡散法, ハンギングドロップ法 詳細: Reservoir: 2M Li2SO4 3% PEG 4K 0.1M MgSO4 0.1 M NaAcetate Protein buffer: 100 mM NaCl, 5 mM LY466195, 1 mM EDTA, 10 mM HEPES pH 7 No added glutamate PH範囲: 5.5
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データ収集
回折
平均測定温度: 100 K
放射光源
由来: シンクロトロン / サイト: APS / ビームライン: 22-ID / 波長: 1 Å
検出器
タイプ: RAYONIX MX300-HS / 検出器: CCD / 日付: 2015年7月1日
放射
プロトコル: SINGLE WAVELENGTH / 単色(M)・ラウエ(L): M / 散乱光タイプ: x-ray
放射波長
波長: 1 Å / 相対比: 1
反射
解像度: 1.8→30 Å / Num. obs: 82330 / % possible obs: 100 % / 冗長度: 14.5 % / Rmerge(I) obs: 0.058 / Net I/σ(I): 48.4
反射 シェル
解像度: 1.8→1.83 Å / 冗長度: 14.2 % / Rmerge(I) obs: 1 / Mean I/σ(I) obs: 2.8 / % possible all: 100