Qin Li, Tang Ling-Hui, Xu Jia-Shu, Zhang Xian-Hui, Zhu Yun, Zhang Chun-Rui, Wang Mei-Hua, Liu Xue-Lei, Li Fei, Sun Fei, Su Min, Zhai Yujia, Chen Yu-Hang
State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China.
Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China.
Sci Adv. 2022 Mar 4;8(9):eabm3238. doi: 10.1126/sciadv.abm3238. Epub 2022 Mar 2.
Aluminum-activated malate transporters (ALMTs) form an anion channel family that plays essential roles in diverse functions in plants. ALMT12, also named QUAC1 (quick anion channel 1), regulates stomatal closure in response to environmental stimuli. However, the molecular basis of ALMT12/QUAC1 activity remains elusive. Here, we describe the cryo-EM structure of ALMT12/QUAC1 from at 3.5-Å resolution. ALMT12/QUAC1 is a symmetrical dimer, forming a single electropositive T-shaped pore across the membrane. The transmembrane and cytoplasmic domains are assembled into a twisted two-layer architecture, with their associated dimeric interfaces nearly perpendicular. ALMT12/QUAC1-mediated currents display rapid kinetics of activation/deactivation and a bell-shaped voltage dependency, reminiscent of the rapid (R)-type anion currents. Our structural and functional analyses reveal a domain-twisting mechanism for malate-mediated activation. Together, our study uncovers the molecular basis for a previously uncharacterized class of anion channels and provides insights into the gating and modulation of the ALMT12/QUAC1 anion channel.
铝激活苹果酸转运蛋白（ALMTs）构成一个阴离子通道家族，在植物的多种功能中发挥着重要作用。ALMT12，也被称为QUAC1（快速阴离子通道1），可响应环境刺激调节气孔关闭。然而，ALMT12/QUAC1活性的分子基础仍然不清楚。在这里，我们描述了来自的ALMT12/QUAC1的冷冻电镜结构，分辨率为3.5埃。ALMT12/QUAC1是一个对称二聚体，在膜上形成一个单一的带正电的T形孔。跨膜结构域和细胞质结构域组装成一个扭曲的两层结构，其相关的二聚体界面几乎垂直。ALMT12/QUAC1介导的电流显示出快速的激活/失活动力学和钟形电压依赖性，类似于快速（R）型阴离子电流。我们的结构和功能分析揭示了苹果酸介导的激活的结构域扭曲机制。总之，我们的研究揭示了一类以前未被表征的阴离子通道的分子基础，并为ALMT12/QUAC1阴离子通道的门控和调节提供了见解。
