Jing Dan, Kong Fang, Lu Xiaoli, Huang Gaoxingyu, Huang Jing, Wang Haolin, Shi Yigong, Wang Chengcheng
College of Life Sciences, Zhejiang University, Hangzhou 310058, China.
Key Laboratory of Structural Biology of Zhejiang Province, School of Life Sciences, Westlake University, Institute of Biology, Westlake Institute for Advanced Study, Hangzhou, Zhejiang Province 310024, China.
Proc Natl Acad Sci U S A. 2025 Aug 5;122(31):e2513424122. doi: 10.1073/pnas.2513424122. Epub 2025 Jul 28.
Indole-3-acetic acid (IAA), the major form of auxin, is essential for plant growth. Auxin resistant 1 (AUX1), the first identified auxin importer, plays a crucial role in polar auxin transport (PAT). Here, we present cryo-EM structures of AUX1 in the IAA-free and IAA-bound states. AUX1 exists as a monomer that contains 11 transmembrane helices (TMs). TMs 1 to 5 and 6 to 10 constitute the two halves of a classic LeuT-fold, and TM11 interacts with both halves at the interface. In the IAA-bound state, IAA is specifically recognized in a central pocket formed by TM1, TM3, TM6, and TM8. In the presence of IAA, TM1 and TM6 undergo marked conformational changes that are critical for IAA transport. His249 stands out to be a key residue for substrate uptake and release. Our structures reveal the molecular basis for AUX1-mediated IAA binding and transport.
吲哚 - 3 - 乙酸（IAA）是生长素的主要形式，对植物生长至关重要。生长素抗性1（AUX1）是首个被鉴定出的生长素输入载体，在生长素极性运输（PAT）中起关键作用。在此，我们展示了AUX1在无IAA状态和IAA结合状态下的冷冻电镜结构。AUX1以单体形式存在，包含11个跨膜螺旋（TM）。TM1至5和TM6至10构成经典亮氨酸转运蛋白（LeuT）折叠的两个半部分，TM11在界面处与这两个半部分相互作用。在IAA结合状态下，IAA在由TM1、TM3、TM6和TM8形成的中央口袋中被特异性识别。在IAA存在的情况下，TM1和TM6发生显著的构象变化，这对IAA运输至关重要。His249是底物摄取和释放的关键残基。我们的结构揭示了AUX1介导的IAA结合和运输的分子基础。
