Molecular mechanism for inhibition of a critical component in the Arabidopsis thaliana abscisic acid signal transduction pathways, SnRK2.6, by protein phosphatase ABI1. Author Tian Xie, Ruobing Ren, Yuan-yuan Zhang, Yuxuan Pang, Chuangye Yan, Xinqi Gong, Yuan He, Wenqi Li, Di Miao, Qi Hao, Haiteng Deng, Zhixin Wang, Jia-Wei Wu, Nieng Yan Publication Year 2012 Type Journal Article 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. Keywords Molecular Sequence Data, Protein Kinases, Signal Transduction, Models, Molecular, Phosphorylation, Protein Structure, Tertiary, Crystallography, X-Ray, Amino Acid Sequence, Enzyme Activation, Arabidopsis, Arabidopsis Proteins, Sequence Deletion, Abscisic Acid, Phosphoprotein Phosphatases Journal J Biol Chem Volume 287 Issue 1 Pages 794-802 Date Published 2012 Jan 02 ISSN Number 1083-351X DOI 10.1074/jbc.M111.313106 Alternate Journal J Biol Chem PMCID PMC3249133 PMID 22090030 PubMedPubMed CentralGoogle ScholarBibTeXEndNote X3 XML