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Publication Abstract from PubMed

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.

Structural Insights into the Abscisic Acid Stereospecificity by the ABA Receptors PYR/PYL/RCAR.,Zhang X, Jiang L, Wang G, Yu L, Zhang Q, Xin Q, Wu W, Gong Z, Chen Z PLoS One. 2013 Jul 2;8(7):e67477. doi: 10.1371/journal.pone.0067477. Print 2013. PMID:23844015^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.