ATP binding by the P-loop NTPase OsYchF1 (an unconventional G protein) contributes to biotic but not abiotic stress responses
ATP binding by the P-loop NTPase OsYchF1 (an unconventional G protein) contributes to biotic but not abiotic stress responses
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P 环 NTPase OsYchF1（一种非常规 G 蛋白）与 ATP 的结合有助于生物应激反应，但不会促进非生物应激反应
DOI：
10.1073/pnas.1522966113
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发表时间：
2016-03-08
影响因子：
11.1
通讯作者：
Lam, Hon-Ming
中科院分区：
文献类型：
--
作者：
Cheung, Ming-Yan;Li, Xiaorong;Lam, Hon-Ming
在所有常规核苷酸中，GTP通常被认为是与G蛋白相关的唯一信号配体。然而，YchF亚家族（一种非常规G蛋白）结合和水解GTP和ATP的能力对ATP结合的作用提出了一个主要问题。通过X-射线晶体学分析，我们发现OsYchF 1与ATP和GTP结合后，其构象发生了不同的变化。排除ATP结合/水解的突变也阻止OsYchF 1作为植物防御反应的负调节因子发挥作用，证明ATP结合/水解在抗病性中的特定作用。这一发现将对我们理解所有生命王国中G蛋白YchF亚家族的结构-功能关系产生重大影响。G蛋白通过其结合和水解GTP的能力参与细胞调节途径的几乎所有方面。有趣的是，YchF亚家族具有结合ATP和GTP的独特能力，并且可能是基于系统发育研究的G蛋白的祖先形式，并且存在于所有生命王国中。然而，这种放松的配体特异性的生物学意义长期以来一直困扰着研究人员。在这里，我们已经阐明了不同的构象变化所造成的结合YchF同源水稻（OsYchF 1）ATP与GTP的X-射线晶体学。此外，通过比较的配体的位置和各种氨基酸残基的晶体结构中的脱辅基结合和配体结合的版本的结合位点的3D关系，揭示了蛋白质的能力，结合两个配体的机制。OsYchF 1的非经典G4基序突变为GTP特异性的经典序列，排除了ATP的结合/水解，并防止OsYchF 1作为植物防御反应的负调节剂发挥作用，同时保留其结合/水解GTP的能力及其作为非生物胁迫反应的负调节剂的功能，证明ATP结合/水解在抗病性中的特定作用。这一发现将对我们理解所有生命王国中G蛋白YchF亚家族的结构-功能关系产生重大影响。
Significance Among all regular nucleotides, GTP is commonly regarded as the sole signaling ligand associated with G proteins. However, the ability of the YchF subfamily (an unconventional G protein) to bind and hydrolyze both GTP and ATP poses a major question on the role of ATP binding. Through X-ray crystallography, we showed the different specific conformational changes caused by the binding of OsYchF1 to ATP versus GTP. A mutation that precludes the binding/hydrolysis of ATP also prevents OsYchF1 from functioning as a negative regulator of plant defense responses, demonstrating the specific role of ATP-binding/hydrolysis in disease resistance. This discovery will have a significant impact on our understanding of the structure–function relationships of the YchF subfamily of G proteins in all kingdoms of life. G proteins are involved in almost all aspects of the cellular regulatory pathways through their ability to bind and hydrolyze GTP. The YchF subfamily, interestingly, possesses the unique ability to bind both ATP and GTP, and is possibly an ancestral form of G proteins based on phylogenetic studies and is present in all kingdoms of life. However, the biological significance of such a relaxed ligand specificity has long eluded researchers. Here, we have elucidated the different conformational changes caused by the binding of a YchF homolog in rice (OsYchF1) to ATP versus GTP by X-ray crystallography. Furthermore, by comparing the 3D relationships of the ligand position and the various amino acid residues at the binding sites in the crystal structures of the apo-bound and ligand-bound versions, a mechanism for the protein’s ability to bind both ligands is revealed. Mutation of the noncanonical G4 motif of the OsYchF1 to the canonical sequence for GTP specificity precludes the binding/hydrolysis of ATP and prevents OsYchF1 from functioning as a negative regulator of plant-defense responses, while retaining its ability to bind/hydrolyze GTP and its function as a negative regulator of abiotic stress responses, demonstrating the specific role of ATP-binding/hydrolysis in disease resistance. This discovery will have a significant impact on our understanding of the structure–function relationships of the YchF subfamily of G proteins in all kingdoms of life.