Mechanism of high-affinity abscisic acid binding to PYL9/RCAR1
Mechanism of high-affinity abscisic acid binding to PYL9/RCAR1
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DOI：
10.1111/gtc.12140
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发表时间：
2014-05-01
期刊：
影响因子：
2.1
通讯作者：
Hakoshima, Toshio
中科院分区：
文献类型：
--
作者：
Nakagawa, Masahiro;Kagiyama, Megumi;Hakoshima, Toshio
拟南芥脱落酸（阿坝）受体是植物适应水分胁迫的关键激素，由14个PYR/PYL/RCAR蛋白组成，分为I、II和III三个亚家族，表明其功能分化。虽然它们的单体-二聚体平衡可能与它们的ABA结合亲和力的差异相关，但二聚化如何降低亲和力尚不清楚。PYL 9是高亲和力亚家族I的代表，与亚家族III的低亲和力成员之间的比较结构和结合研究表明，非极性三联体（Ile 110，Val 162和Leu 165）和Pro64有助于通过诱导阿坝羧基的移位与保守的Asn 169形成额外的直接氢键来增强ABA结合亲和力。我们的突变研究PYL 1成功地产生了单体突变体PYL 1表现出低阿坝亲和力，也表现出高ABA结合亲和力的二聚体突变体PYL 1，这表明阿坝受体的二聚体形成是不是必不可少的低ABA结合亲和力。我们的研究有助于建立更高的ABA结合亲和力的亚家族受体的结构基础，并提供了一个线索，了解植物中的激素作用的广谱表现出不同的ABA结合亲和力的多种受体。
Arabidopsis 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.