title: Molecular mechanism for inhibition of a critical component in the Arabidopsis thaliana abscisic acid signal transduction pathways, SnRK2.6, by protein phosphatase ABI1.
abstract: Subclass III SnRK2s (SnRK2.6/2.3/2.2) are the key positive regulators of abscisic acid (ABA) signal transduction in Arabidopsis thaliana. The kinases, activated by ABA or osmotic stress, phosphorylate stress-related transcription factors and ion channels, which ultimately leads to the protection of plants from dehydration or high salinity. In the absence of stressors, SnRK2s are subject to negative regulation by group A protein phosphatase type 2Cs (PP2C), whereas the underlying molecular mechanism remains to be elucidated. Here we report the crystal structure of the kinase domain of SnRK2.6 at 2.6-Å resolution. Structure-guided biochemical analyses identified two distinct interfaces between SnRK2.6 and ABI1, a member of group A PP2Cs. Structural modeling suggested that the two interfaces lock SnRK2.6 and ABI1 in an orientation such that the activation loop of SnRK2.6 is posited to the catalytic site of ABI1 for dephosphorylation. These studies revealed the molecular basis for PP2Cs-mediated inhibition of SnRK2s and provided important insights into the downstream signal transduction of ABA.
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Medicine and School of Life Sciences, Beijing, 100084, China; Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Tian
authors.initials: T
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Medicine and School of Life Sciences, Beijing, 100084, China; Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Ruobing
authors.initials: R
authors.lastname: Ren
authors.affiliation: Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Medicine and School of Life Sciences, Beijing, 100084, China; Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Yuxuan
authors.initials: Y
authors.lastname: Pang
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Medicine and School of Life Sciences, Beijing, 100084, China; Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Chuangye
authors.initials: C
authors.lastname: Yan
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Medicine and School of Life Sciences, Beijing, 100084, China; Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Xinqi
authors.initials: X
authors.lastname: Gong
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Medicine and School of Life Sciences, Beijing, 100084, China; Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: He
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Medicine and School of Life Sciences, Beijing, 100084, China; Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Wenqi
authors.initials: W
authors.lastname: Li
authors.affiliation: School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Di
authors.initials: D
authors.lastname: Miao
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Medicine and School of Life Sciences, Beijing, 100084, China; Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Hao
authors.affiliation: School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Haiteng
authors.initials: H
authors.lastname: Deng
authors.affiliation: School of Medicine and School of Life Sciences, Beijing 100084, China.
authors.forename: Zhixin
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China. Electronic address: jiaweiwu@tsinghua.edu.cn.
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, School of Medicine and School of Life Sciences, Beijing, 100084, China; Tsinghua-Peking Center for Life Sciences, Center for Structural Biology; School of Medicine and School of Life Sciences, Beijing 100084, China. Electronic address: nyan@tsinghua.edu.cn.
authors.forename: Nieng
authors.initials: N
authors.lastname: Yan
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D000040:Abscisic Acid; D011494:Protein Kinases; C472139:OST1 protein, Arabidopsis; C087434:ABI1 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases
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