title: Structural insights into the abscisic acid stereospecificity by the ABA receptors PYR/PYL/RCAR.
abstract: The phytohormone abscisic acid ((+)-ABA) plays a key role in many processes. The biological and biochemical activities of unnatural (-)-ABA have been extensively investigated since 1960s. However, the recognition mechanism by which only a few members among PYR/PYL/RCAR (PYLs) family can bind (-)-ABA remains largely unknown. Here we systematically characterized the affinity of PYLs binding to the (-)-ABA and reported the crystal structures of apo-PYL5, PYL3-(-)-ABA and PYL9-(+)-ABA. PYL5 showed the strongest binding affinity with (-)-ABA among all the PYLs. PYL9 is a stringently exclusive (+)-ABA receptor with interchangeable disulfide bonds shared by a subclass of PYLs. PYL3 is a dual receptor to both ABA enantiomers. The binding orientation and pocket of (-)-ABA in PYLs are obviously different from those of (+)-ABA. Steric hindrance and hydrophobic interaction are the two key factors in determining the stereospecificity of PYLs binding to (-)-ABA, which is further confirmed by gain-of-function and loss-of-function mutagenesis. Our results provide novel insights of the bioactivity of ABA enantiomers onto PYLs, and shed light on designing the selective ABA receptors agonists.
authors.affiliation: State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, China.
authors.forename: Xingliang
authors.initials: X
authors.lastname: Zhang
authors.forename: Lun
authors.initials: L
authors.lastname: Jiang
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Wang
authors.forename: Lin
authors.initials: L
authors.lastname: Yu
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
authors.forename: Qi
authors.initials: Q
authors.lastname: Xin
authors.forename: Wei
authors.initials: W
authors.lastname: Wu
authors.forename: Zhizhong
authors.initials: Z
authors.lastname: Gong
authors.forename: Zhongzhou
authors.initials: Z
authors.lastname: Chen
mesh_terms: D000040:Abscisic Acid / Q000737:chemistry*; D017360:Arabidopsis / Q000737:chemistry* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D062105:Molecular Docking Simulation; D010937:Plant Growth Regulators / Q000737:chemistry*; D054730:Protein Interaction Domains and Motifs; D011956:Receptors, Cell Surface / Q000737:chemistry* / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D015398:Signal Transduction; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D010937:Plant Growth Regulators; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D000040:Abscisic Acid