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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Structural asymmetry in the magnesium channel CorA points to sequential allosteric regulation
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Structural asymmetry in the magnesium channel CorA points to sequential allosteric regulation

机译:镁通道CorA中的结构不对称指向连续的变构调节

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摘要

Magnesium ions (Mg~(2+)) are essential for life, but the mechanisms regulating their transport into and out of cells remain poorly understood. The CorA-Mrs2-Alr1 superfamily of Mg~(2+) channels represents the most prevalent group of proteins enabling Mg~(2+) ions to cross membranes. Thermotoga maritima CorA (TmCorA) is the only member of this protein family whose complete 3D fold is known. Here, we report the crystal structure of a mutant in the presence and absence of divalent ions and compare it with previous divalent ion-bound TmCorA structures. With Mg~(2+) present, this structure shows binding of a hydrated Mg~(2+) ion to the peri-plasmic Gly-Met-Asn (GMN) motif, revealing clues of ion selectivity in this unique channel family. In the absence of Mg~(2+), TmCorA displays an unexpected asymmetric conformation caused by radial and lateral tilts of protomers that leads to bending of the central, pore-lining helix. Molecular dynamics simulations support these movements, including a bell-like deflection. Mass spectrometric analysis confirms that major proteolytic cleavage occurs within a region that is selectively exposed by such a bell-like bending motion. Our results point to a sequential allosteric model of regulation, where intracellular Mg~(2+) binding locks TmCorA in a symmetric, transport-incompetent conformation and loss of intracellular Mg~(2+) causes an asymmetric, potentially influx-competent conformation of the channel.
机译:镁离子(Mg〜(2+))是生命必不可少的,但调节其进入细胞和从细胞中迁移的机制仍知之甚少。 Mg〜(2+)通道的CorA-Mrs2-Alr1超家族代表使Mg〜(2+)离子能够跨膜的最普遍的蛋白质。 maritoma CorA(TmCorA)是该蛋白家族中唯一已知其完整3D折叠的成员。在这里,我们报告存在和不存在二价离子的突变体的晶体结构,并将其与以前的二价离子结合的TmCorA结构进行比较。在存在Mg〜(2+)的情况下,该结构显示了水合Mg〜(2+)离子与周质Gly-Met-Asn(GMN)基序的结合,从而揭示了该独特通道家族中离子选择性的线索。在没有Mg〜(2+)的情况下,TmCorA会显示出一个由于预知子的径向和横向倾斜而导致的意外的不对称构象,从而导致中心的带孔衬里螺旋弯曲。分子动力学模拟支持这些运动,包括钟形偏转。质谱分析证实,主要的蛋白水解裂解发生在通过这种钟形弯曲运动而选择性暴露的区域内。我们的结果指向了顺序的变构调节模型,其中细胞内Mg〜(2+)结合将TmCorA锁定在对称的,运输不适合的构象中,而细胞内Mg〜(2+)的丢失导致不对称的,可能具有流入能力的构象。这个频道。

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  • 作者单位

    Departments of Biochemistry, University of Toronto, Toronto, ON, Canada, M5G 1L7,Ontario Cancer Institute/Princess Margaret Cancer Centre, Campbell Family Institute for Cancer Research, Toronto, ON, Canada, M5G 1L7;

    Departments of Biochemistry, University of Toronto, Toronto, ON, Canada, M5G 1L7;

    Program in Molecular Structure and Function, Hospital for Sick Children, Toronto, ON, Canada, M5G 1X8;

    Ontario Cancer Institute/Princess Margaret Cancer Centre, Campbell Family Institute for Cancer Research, Toronto, ON, Canada, M5G 1L7,Departments of Medical Biophysics, University of Toronto, Toronto, ON, Canada, M5G 1L7,Department of Structural Biology, Genentech Inc., South San Francisco, CA 94080;

    Departments of Biochemistry, University of Toronto, Toronto, ON, Canada, M5G 1L7,Program in Molecular Structure and Function, Hospital for Sick Children, Toronto, ON, Canada, M5G 1X8;

    Departments of Biochemistry, University of Toronto, Toronto, ON, Canada, M5G 1L7,Ontario Cancer Institute/Princess Margaret Cancer Centre, Campbell Family Institute for Cancer Research, Toronto, ON, Canada, M5G 1L7,Departments of Medical Biophysics, University of Toronto, Toronto, ON, Canada, M5G 1L7,Departments of Molecular Genetics, University of Toronto, Toronto, ON, Canada, M5G 1L7;

  • 收录信息 美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    crystallography; gating; limited proteolysis; pentamer;

    机译:晶体学门控有限的蛋白水解;五聚体;

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