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. 2025 Aug 5;122(31):e2513424122.
doi: 10.1073/pnas.2513424122. Epub 2025 Jul 28.

Structural basis of auxin binding and transport by Arabidopsis thaliana AUX1

Dan Jing #  1   2   3 , Fang Kong #  4 , Xiaoli Lu  2   3 , Gaoxingyu Huang  2   3 , Jing Huang  2   3 , Haolin Wang  2   3 , Yigong Shi  2   3   4 , Chengcheng Wang  2   3
Affiliations

Structural basis of auxin binding and transport by Arabidopsis thaliana AUX1

Dan Jing et al. Proc Natl Acad Sci U S A. .

Abstract

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 Arabidopsis thaliana 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.

Keywords: AUX1; IAA; cryo-EM structure; polar auxin transport.

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Conflict of interest statement

Competing interests statement:The authors declare no competing interest.

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