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Structural basis of salicylic acid perception by Arabidopsis NPR proteins
Nature ( IF 64.8 ) Pub Date : 2020-08-12 , DOI: 10.1038/s41586-020-2596-y
Wei Wang 1, 2 , John Withers 3 , Heng Li 1, 4 , Paul J Zwack 3 , Domnița-Valeria Rusnac 1 , Hui Shi 1 , Lijing Liu 3, 5 , Shunping Yan 3, 6 , Thomas R Hinds 1 , Mikelos Guttman 7 , Xinnian Dong 3 , Ning Zheng 1
Affiliation  

Salicylic acid (SA) is a plant hormone that is critical for resistance to pathogens1–3. The NPR proteins have previously been identified as SA receptors4–10, although how they perceive SA and coordinate hormonal signalling remain unknown. Here we report the mapping of the SA-binding core of Arabidopsis thaliana NPR4 and its ligand-bound crystal structure. The SA-binding core domain of NPR4 refolded with SA adopts an α-helical fold that completely buries SA in its hydrophobic core. The lack of a ligand-entry pathway suggests that SA binding involves a major conformational remodelling of the SA-binding core of NPR4, which we validated using hydrogen–deuterium-exchange mass spectrometry analysis of the full-length protein and through SA-induced disruption of interactions between NPR1 and NPR4. We show that, despite the two proteins sharing nearly identical hormone-binding residues, NPR1 displays minimal SA-binding activity compared to NPR4. We further identify two surface residues of the SA-binding core, the mutation of which can alter the SA-binding ability of NPR4 and its interaction with NPR1. We also demonstrate that expressing a variant of NPR4 that is hypersensitive to SA could enhance SA-mediated basal immunity without compromising effector-triggered immunity, because the ability of this variant to re-associate with NPR1 at high levels of SA remains intact. By revealing the structural mechanisms of SA perception by NPR proteins, our work paves the way for future investigation of the specific roles of these proteins in SA signalling and their potential for engineering plant immunity. Structural determination of the salicylic-acid-binding core of Arabidopsis NPR4 sheds light on the mechanisms through which this plant hormone interacts with its receptors, providing insights that are of potential use in engineering enhanced immunity.

中文翻译:

拟南芥 NPR 蛋白感知水杨酸的结构基础

水杨酸 (SA) 是一种植物激素,对抵抗病原体 1-3 至关重要。NPR 蛋白以前被鉴定为 SA 受体 4-10,尽管它们如何感知 SA 和协调激素信号传导仍然未知。在这里,我们报告了拟南芥 NPR4 的 SA 结合核心及其配体结合晶体结构的映射。用 SA 重新折叠的 NPR4 的 SA 结合核心结构域采用 α-螺旋折叠,将 SA 完全掩埋在其疏水核心中。缺乏配体进入途径表明 SA 结合涉及 NPR4 的 SA 结合核心的主要构象重塑,我们使用全长蛋白质的氢-氘交换质谱分析和通过 SA 诱导的破坏验证了这一点NPR1 和 NPR4 之间的相互作用。我们表明,尽管这两种蛋白质共享几乎相同的激素结合残基,但与 NPR4 相比,NPR1 显示出最小的 SA 结合活性。我们进一步鉴定了 SA 结合核心的两个表面残基,其突变可以改变 NPR4 的 SA 结合能力及其与 NPR1 的相互作用。我们还证明,表达对 SA 过敏的 NPR4 变体可以增强 SA 介导的基础免疫,而不会损害效应触发的免疫,因为这种变体在高水平 SA 下与 NPR1 重新结合的能力保持不变。通过揭示 NPR 蛋白感知 SA 的结构机制,我们的工作为未来研究这些蛋白质在 SA 信号传导中的特定作用及其工程植物免疫的潜力铺平了道路。
更新日期:2020-08-12
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