Structural and biochemical studies identify tobacco SABP2 as a methyl salicylate esterase and implicate it in plant innate immunity
Structural and biochemical studies identify tobacco SABP2 as a methyl salicylate esterase and implicate it in plant innate immunity
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DOI：
10.1073/pnas.0409227102
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发表时间：
2005-02-01
影响因子：
11.1
通讯作者：
Tong, L
中科院分区：
文献类型：
--
作者：
Forouhar, F;Yang, Y;Tong, L
水杨酸（SA）是激活植物防御病原体感染反应的关键信号。我们最近从烟草中鉴定出 SA 结合蛋白 2 (SABP2)，它是一种对 SA 表现出高亲和力的蛋白质，在激活植物病原体的系统获得性抗性中发挥着至关重要的作用。在这里，我们以高达 2.1 埃的分辨率报告了单独的 SABIP2 以及与 SA 复合的 SABIP2 的晶体结构。该结构证实 SABP2 是 α/β 水解酶超家族的成员，以 Ser-81、His-238 和 Asp-210 作为催化三联体。 SA 结合在活性位点并完全与溶剂隔离，这与该化合物对 SABP2 的高亲和力一致。我们的生化研究表明，SABP2 以水杨酸甲酯为底物具有很强的酯酶活性，并且 SA 是该催化作用的有效产物抑制剂。 SABP2 与 MeSA 在活性位点的建模与所有这些生化观察结果一致。我们的结果表明，SABP2 可能需要将 MeSA 转化为 SA，作为信号转导途径的一部分，激活系统获得性抵抗，或许还可能激活局部防御反应。
Salicylic acid (SA) is a critical signal for the activation of plant defense responses against pathogen infections. We recently identified SA-binding protein 2 (SABP2) from tobacco as a protein that displays high affinity for SA and plays a crucial role in the activation of systemic acquired resistance to plant pathogens. Here we report the crystal structures of SABIP2, alone and in complex with SA at up to 2.1-Angstrom resolution. The structures confirm that SABP2 is a member of the alpha/beta hydrolase superfamily of enzymes, with Ser-81, His-238, and Asp-210 as the catalytic triad. SA is bound in the active site and is completely shielded from the solvent, consistent with the high affinity of this compound for SABP2. Our biochemical studies reveal that SABP2 has strong esterase activity with methyl salicylate as the substrate, and that SA is a potent product inhibitor of this catalysis. Modeling of SABP2 with MeSA in the active site is consistent with all these biochemical observations. Our results suggest that SABP2 may be required to convert MeSA to SA as part of the signal transcluction pathways that activate systemic acquired resistance and perhaps local defense responses as well.