title: Structural insights into the mechanism of abscisic acid signaling by PYL proteins.
abstract: Abscisic acid (ABA) is an important phytohormone that regulates plant stress responses. Proteins from the PYR-PYL-RCAR family were recently identified as ABA receptors. Upon binding to ABA, a PYL protein associates with type 2C protein phosphatases (PP2Cs) such as ABI1 and ABI2, inhibiting their activity; the molecular mechanisms by which PYLs mediate ABA signaling remain unknown, however. Here we report three crystal structures: apo-PYL2, (+)-ABA-bound PYL2 and (+)-ABA-bound PYL1 in complex with phosphatase ABI1. Apo-PYL2 contains a pocket surrounded by four highly conserved surface loops. In response to ABA binding, loop CL2 closes onto the pocket, creating a surface that recognizes ABI1. In the ternary complex, the CL2 loop is located near the active site of ABI1, blocking the entry of substrate proteins. Together, our data reveal the mechanisms by which ABA regulates PYL-mediated inhibition of PP2Cs.
authors.affiliation: State Key Laboratory of Bio-membrane and Membrane Biotechnology, TsinghuaUniversity, Beijing, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Yin
authors.forename: He
authors.initials: H
authors.lastname: Fan
authors.forename: Qi
authors.initials: Q
authors.lastname: Hao
authors.forename: Xiaoqiu
authors.initials: X
authors.lastname: Yuan
authors.forename: Di
authors.initials: D
authors.lastname: Wu
authors.forename: Yuxuan
authors.initials: Y
authors.lastname: Pang
authors.forename: Chuangye
authors.initials: C
authors.lastname: Yan
authors.forename: Wenqi
authors.initials: W
authors.lastname: Li
authors.forename: Jiawei
authors.initials: J
authors.lastname: Wang
authors.forename: Nieng
authors.initials: N
authors.lastname: Yan
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D008954:Models, Biological; D008958:Models, Molecular; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010937:Plant Growth Regulators / Q000378:metabolism*; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D010937:Plant Growth Regulators; D000040:Abscisic Acid; C087434:ABI1 protein, Arabidopsis; D010749:Phosphoprotein Phosphatases