Cryo-EM Structures of the Magnesium Channel CorA Reveal Symmetry Break upon Gating.
Cryo-EM Structures of the Magnesium Channel CorA Reveal Symmetry Break upon Gating.
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DOI：
10.1016/j.cell.2015.12.055
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发表时间：
2016-02-11
期刊：
影响因子：
64.5
通讯作者：
Subramaniam S
中科院分区：
文献类型：
--
作者：
Matthies D;Dalmas O;Borgnia MJ;Dominik PK;Merk A;Rao P;Reddy BG;Islam S;Bartesaghi A;Perozo E;Subramaniam S
CORA是原核生物中主要的镁摄取系统，受细胞内镁离子(Kd~1-2 mM)的调控。X射线结晶学研究表明，在镁离子结合和无镁离子条件下，CORA的构象相似，但EPR光谱研究揭示了由镁离子驱动的四元构象的巨大变化。在此，我们分别在3.8A、7.1A和7.1A的分辨率下测定了CoLa的闭合构象和两个不含镁离子的“开放”态的低温EM结构。在没有结合镁离子的情况下，5个亚基中的4个在柄螺旋上的铰链状运动导致不同程度的位移(~10~~25A)，最大可达~35°。因此，在单一的5重对称闭合态和低镁离子、开放、不对称构象态的系综之间的转变是CORA门的关键结构特征。这一机制很可能适用于其他结构相似的二价离子通道。
CorA, the major Mg2+ uptake system in prokaryotes, is gated by intracellular Mg2+ (KD ~1–2 mM). X-ray crystallographic studies of CorA show similar conformations under Mg2+-bound and Mg2+-free conditions, but EPR spectroscopic studies reveal large Mg2+-driven quaternary conformational changes. Here, we determined cryo-EM structures of CorA in the Mg2+-bound “closed” conformation and in two “open” Mg2+-free states at resolutions of 3.8 A, 7.1 A and 7.1 A, respectively. In the absence of bound Mg2+, four of the five subunits are displaced to variable extents (~10 to ~25 A) by hinge-like motions at the stalk helix as large as ~35°. The transition between a single 5-fold symmetric closed state and an ensemble of low Mg2+, open, asymmetric conformational states, is thus the key structural signature of CorA gating. This mechanism is likely to apply to other structurally similar divalent ion channels.
影响因子：
3.4
作者：
Svidova, Soria;Sponder, Gerhard;Schweyen, Rudolf J.;Djinovic-Carugo, Kristina
通讯作者：
Djinovic-Carugo, Kristina