A nucleotide phosphatase activity in the nucleotide binding domain of an orphan resistance protein from rice.
A nucleotide phosphatase activity in the nucleotide binding domain of an orphan resistance protein from rice.
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DOI：
10.1074/jbc.m111.314450
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发表时间：
2012-02-03
期刊：
影响因子：
--
通讯作者：
Cann MJ
中科院分区：
文献类型：
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作者：
Fenyk S;Campillo Ade S;Pohl E;Hussey PJ;Cann MJ
背景：植物抗性蛋白是植物应答病原菌的分子开关。结果：耐药蛋白的一个子集具有核苷酸磷酸酶活性。结论：耐药蛋白的信号传导模式比以前推测的更加多样化。意义：陆生植物可能进化出了新的生物化学活性来抵抗病原体的攻击。植物抗性蛋白（R蛋白）是植物免疫系统的关键组成部分，可响应多种不同病原体而被激活。R蛋白是P环NTR超家族成员，目前的模型描述了它们在防御信号通路中的主要功能。在这里，我们表明，一个子集的R-蛋白已经进化出一种新的功能，以打击病原体感染。这类R蛋白在核苷酸结合结构域中具有核苷酸磷酸酶活性。落在相同系统发育分支中的相关R-蛋白都显示出相同的核苷酸磷酸酶活性，表明至少在R-蛋白的子集内具有保守的功能。R蛋白核苷酸磷酸酶催化核苷酸以单磷酸核苷酸为底物合成核苷。保守的催化残基的突变大大降低了活性，与P-环NTPases的生物化学一致。动力学分析，分析凝胶过滤，和化学交联表明，核苷酸结合结构域作为一个多聚体是活跃的。核磁共振和核苷酸类似物鉴定了末端磷酸键作为反应的目标，该反应利用了水对磷酸酯的金属介导亲核攻击。总之，我们已经确定了一组具有独特功能的R蛋白。这种生物化学活性似乎与植物在旨在抵抗病原体攻击的信号通路中共同进化。
Background: Plant resistance proteins are molecular switches that respond to plant pathogens. Results: A subset of resistance proteins has a nucleotide phosphatase activity. Conclusion: The modes of signaling behavior in resistance proteins are more diverse than previously suspected. Significance: Novel biochemical activities might have evolved in land plants to resist pathogen attack. Plant resistance proteins (R-proteins) are key components of the plant immune system activated in response to a plethora of different pathogens. R-proteins are P-loop NTPase superfamily members, and current models describe their main function as ATPases in defense signaling pathways. Here we show that a subset of R-proteins have evolved a new function to combat pathogen infection. This subset of R-proteins possesses a nucleotide phosphatase activity in the nucleotide-binding domain. Related R-proteins that fall in the same phylogenetic clade all show the same nucleotide phosphatase activity indicating a conserved function within at least a subset of R-proteins. R-protein nucleotide phosphatases catalyze the production of nucleoside from nucleotide with the nucleotide monophosphate as the preferred substrate. Mutation of conserved catalytic residues substantially reduced activity consistent with the biochemistry of P-loop NTPases. Kinetic analysis, analytical gel filtration, and chemical cross-linking demonstrated that the nucleotide-binding domain was active as a multimer. Nuclear magnetic resonance and nucleotide analogues identified the terminal phosphate bond as the target of a reaction that utilized a metal-mediated nucleophilic attack by water on the phosphoester. In conclusion, we have identified a group of R-proteins with a unique function. This biochemical activity appears to have co-evolved with plants in signaling pathways designed to resist pathogen attack.