3w9r
From Proteopedia
Crystal structure of the high-affinity abscisic acid receptor PYL9/RCAR9 bound to ABA
Structural highlights
FunctionPYL9_ARATH Receptor for abscisic acid (ABA) required for ABA-mediated responses such as stomatal closure and germination inhibition. Inhibits the activity of group-A protein phosphatases type 2C (PP2Cs) when activated by ABA. Confers enhanced sensitivity to ABA.[1] Publication Abstract from PubMedArabidopsis receptors of abscisic acid (ABA), the key plant hormone for adaptation to water stress, comprise 14 PYR/PYLs/RCARs proteins classified into three subfamilies I, II, and III, which suggests functional differentiation. Although their monomer-dimer equilibria may be correlated with differences in their ABA-binding affinities, how the dimerization decreases the affinity is unclear. Comparative structural and binding studies between PYL9, which is a representative of high-affinity subfamily I, and low-affinity members of subfamily III reveals that the nonpolar triplet (Ile110, Val162, and Leu165) and Pro64 contribute to enhance ABA-binding affinity by inducing a shift of the ABA carboxyl group to form additional direct hydrogen bonds with conserved Asn169. Our mutation studies of PYL1 successfully produced a monomeric mutant PYL1 exhibiting low ABA affinity and also a dimeric mutant PYL1 exhibiting high ABA-binding affinity, suggesting that dimer formation of ABA receptors is not essential for their low ABA-binding affinity. Our study contributes toward establishing the structural basis for the higher ABA-binding affinity of the subfamily receptors and provides a clue for understanding the broad spectrum of hormone actions in plants manifested by the different hormone-binding affinity of multiple receptors. Mechanism of high-affinity abscisic acid binding to PYL9/RCAR1.,Nakagawa M, Kagiyama M, Shibata N, Hirano Y, Hakoshima T Genes Cells. 2014 Mar 19. doi: 10.1111/gtc.12140. PMID:24645846[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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