Cryo-EM structure of OSCA1.2 from Oryza sativa elucidates the mechanical basis of potential membrane hyperosmolality gating
Cryo-EM structure of OSCA1.2 from Oryza sativa elucidates the mechanical basis of potential membrane hyperosmolality gating
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DOI：
10.1073/pnas.1900774116
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发表时间：
2019-07-09
影响因子：
11.1
通讯作者：
Stowell, Michael H. B.
中科院分区：
文献类型：
--
作者：
Maity, Koustav;Heumann, John M.;Stowell, Michael H. B.
植物对水分胁迫和渗透胁迫的感知和响应是植物生长、发育和生存的关键。最近，在拟南芥中发现了一种渗透压敏感离子通道，称为OSCA 1，其在高渗透压环境中起作用。在这里，我们报告的冷冻电子显微镜（cryoEM）的结构和功能的OSCA 1同源水稻（水稻; OsOSCA1.2），导致一个模型，它可以介导高渗透压传感和运输途径门控。结构显示为二聚体;每个亚基的分子结构由11个跨膜（TM）螺旋和与RNA识别蛋白具有同源性的胞质可溶性结构域组成。TM结构域在结构上与钙依赖性离子通道和脂质乱序酶的TMEM 16家族相关。胞质可溶性结构域具有独特的结构特征，其形式为平行于质膜的延伸的胞内螺旋臂。这些螺旋臂被很好地定位以潜在地感测由膨压变化引起的脂质双层的内小叶上的侧向张力。计算动力学分析表明，该结构域如何耦合到分子的TM部分，以打开运输途径。氢/氘交换质谱（HDXMS）实验证实了这些耦合域的构象动力学。这些研究提供了一个框架，以了解拟议的高渗透压传感在主食作物植物的结构基础，扩展我们的知识的anoctamin超家族重要的植物和真菌，并提供了一个潜在的翻译膜压力运输调节的结构机制。
Sensing and responding to environmental water deficiency and osmotic stresses are essential for the growth, development, and survival of plants. Recently, an osmolality-sensing ion channel called OSCA1 was discovered that functions in sensing hyperosmolality in Arabidopsis. Here, we report the cryo-electron microscopy (cryoEM) structure and function of an OSCA1 homolog from rice (Oryza sativa; OsOSCA1.2), leading to a model of how it could mediate hyperosmolality sensing and transport pathway gating. The structure reveals a dimer; the molecular architecture of each subunit consists of 11 transmembrane (TM) helices and a cytosolic soluble domain that has homology to RNA recognition proteins. The TM domain is structurally related to the TMEM16 family of calciumdependent ion channels and lipid scramblases. The cytosolic soluble domain possesses a distinct structural feature in the form of extended intracellular helical arms that are parallel to the plasma membrane. These helical arms are well positioned to potentially sense lateral tension on the inner leaflet of the lipid bilayer caused by changes in turgor pressure. Computational dynamic analysis suggests how this domain couples to the TM portion of the molecule to open a transport pathway. Hydrogen/deuterium exchange mass spectrometry (HDXMS) experimentally confirms the conformational dynamics of these coupled domains. These studies provide a framework to understand the structural basis of proposed hyperosmolality sensing in a staple crop plant, extend our knowledge of the anoctamin superfamily important for plants and fungi, and provide a structural mechanism for potentially translating membrane stress to transport regulation.