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Molecular basis for the R-type anion channel QUAC1 activity in guard cells
bioRxiv - Plant Biology Pub Date : 2021-09-10 , DOI: 10.1101/2021.09.09.459598
Li Qin , Lin-hui Tang , Jia-shu Xu , Xian-hui Zhang , Yun Zhu , Chun-rui Zhang , Xue-lei Liu , Mei-hua Wang , Fei Li , Fei Sun , Min Su , Yu-Jia Zhai , Yu-hang Chen

The rapid (R)-type anion channel plays a central role in controlling stomatal closure in plant guard cells, thus regulating the exchange of water and photosynthetic gas (CO2) in response to environmental stimuli. The activity of the R- type anion channel is regulated by malate. However, the molecular basis of the R-type anion channel activity remains elusive. Here, we describe the first cryo-EM structure of the R-type anion channel QUAC1 at 3.5 Å resolution in the presence of malate. The structure reveals that the QUAC1 is a symmetrical dimer, forming a single electropositive T-shaped pore for passing anions across the membrane. The transmembrane and cytoplasmic domains are assembled into a twisted bi-layer architecture, with the associated dimeric interfaces nearly perpendicular. Our structural and functional analyses reveal that QUAC1 functions as an inward rectifying anion channel and suggests a mechanism for malate-mediated channel activation. Altogether, our study uncovers the molecular basis for a novel class of anion channels and provides insights into the gating and modulation of the R-type anion channel.

中文翻译:

保卫细胞中 R 型阴离子通道 QUAC1 活性的分子基础

快速 (R) 型阴离子通道在控制植物保卫细胞的气孔关闭方面起着核心作用,从而调节水和光合气体 (CO 2) 以响应环境刺激。R-型阴离子通道的活性受苹果酸调节。然而,R 型阴离子通道活性的分子基础仍然难以捉摸。在这里,我们描述了在苹果酸存在下,分辨率为 3.5 Å 的 R 型阴离子通道 QUAC1 的第一个冷冻电镜结构。该结构表明 QUAC1 是一个对称的二聚体,形成一个单一的正电 T 形孔,用于使阴离子穿过膜。跨膜结构域和细胞质结构域组装成扭曲的双层结构,相关的二聚体界面几乎垂直。我们的结构和功能分析表明,QUAC1 作为内向整流阴离子通道发挥作用,并提出了苹果酸介导的通道激活机制。共,
更新日期:2021-09-13
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