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LETTERS TO THE EDITOR

Cryo-EM structure of the hyperpolarization-activated inwardly rectifying potassium channel KAT1 from Arabidopsis

Siyu Li¹ , Fan Yang¹ , Demeng Sun^1,* , Yong Zhang¹ , Mengge Zhang¹ , Sanling Liu¹ , Peng Zhou² , Chaowei Shi¹ , Longhua Zhang^1,* , Changlin Tian^1,2,*

¹Hefei National Laboratory of Physical Sciences at Microscale, Anhui Laboratory of Advanced Photonic Science and Technology and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
²High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230030, China
These authors contributed equally: Siyu Li, Fan Yang, Demeng Sun, Yong Zhang
* Correspondence: Demeng Sun(dmsun@ustc.edu.cn)Longhua Zhang(zlhustc@ustc.edu.cn)Changlin Tian(cltian@ustc.edu.cn)

Dear Editor,

Plants utilize K+ ions to maintain hydrostatic pressure, drive irreversible cell expansion for growth, and facilitate reversible changes in guard cell volume that cause stomatal opening or closing. KAT1 is a voltage-dependent potassium channel from Arabidopsis thaliana that is mainly expressed in guard cells. KAT1 allows the influx of K+, leading to the swelling and opening of the stoma, and therefore plays a key role in regulating the aperture of stomatal pores on the surface of plant leaves.1,2,3 To understand the gating mechanism of plant K+ channels poses several challenges, despite many structural similarities between these plant K+ channels and mammalian Kv and Shaker channels.4 Remarkably, most voltage-gated ion channels, such as Na+ (Nav), Ca2+ (Cav), and K+ (Kv) channels, open when the cell membrane is depolarized (when the voltage is positive inside relative to outside). Comparing with conventional depolarized K+ channels, KAT1 has a uniquely reversed voltage dependence: depolarization causes closing, and hyperpolarization causes opening.3 KAT1 thus falls into a rare class of hyperpolarization-activated channels, which include hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels in animals, and KAT and AKT channels in plants.

https://doi.org/10.1038/s41422-020-00407-3

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