Structural basis for cytokinin recognition by Arabidopsis thaliana histidine kinase 4


Cytokinins are classic hormones that orchestrate plant growth and development and the integrity of stem cell populations. Cytokinin receptors are eukaryotic sensor histidine kinases that are activated by both naturally occurring adenine-type cytokinins and urea-based synthetic compounds. Crystal structures of the Arabidopsis thaliana histidine kinase 4 sensor domain in complex with different cytokinin ligands now rationalize the hormone-binding specificity of the receptor and may spur the design of new cytokinin ligands.

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Figure 1: AHK4 binds cytokinins with its membrane-distal PAS domain.
Figure 2: Structural plasticity in the AHK4 PAS domain allows for the binding of diverse cytokinins.
Figure 3: Urea-based synthetic cytokinins mimic adenine-type hormone-receptor interactions.

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We thank T. Mizuno for providing plasmid pCold IV–AHK4 and strain KMI001, M. Jinek and Y. Jaillais for comments on the manuscript and W. Kwiatkowski and staff at beamlines BL 8.2.1 and 8.2.2 of the Advanced Light Source in Berkeley, California, for technical support. This work was supported by long-term fellowships from the European Molecular Biology Organization, the International Human Frontier Science Program Organization and the Marc and Eva Stern foundation (M.H.) and by grants from the US National Institutes of Health (NIH) (5R01GM52413), the US National Science Foundation (IOS-0649389) and the Howard Hughes Medical Institute (J.C.). Maintenance of the Salk X-ray equipment is supported by NIH grant P30 NS057096.

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M.H. designed the project; M.H. and T.D. expressed and purified proteins and carried out functional assays; M.H. crystallized, phased and refined the structures; M.H. analyzed the data; J.C. supervised the project; and M.H. wrote the paper.

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Correspondence to Joanne Chory.

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The authors declare no competing financial interests.

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Hothorn, M., Dabi, T. & Chory, J. Structural basis for cytokinin recognition by Arabidopsis thaliana histidine kinase 4. Nat Chem Biol 7, 766–768 (2011).

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