Landrieu Isabelle, da Costa Marco, De Veylder Lieven, Dewitte Frédérique, Vandepoele Klaas, Hassan Sahar, Wieruszeski Jean-Michel, Corellou Florence, Faure Jean-Denis, Van Montagu Marc, Inzé Dirk, Lippens Guy
Unité Mixte de Recherche 8525 Centre National de la Recherche Scientifique-Lille2, Institut de Biologie de Lille/Pasteur Institute of Lille, 59019 Lille Cedex, France.
Proc Natl Acad Sci U S A. 2004 Sep 7;101(36):13380-5. doi: 10.1073/pnas.0405248101. Epub 2004 Aug 25.
The dual-specificity CDC25 phosphatases are critical positive regulators of cyclin-dependent kinases (CDKs). Even though an antagonistic Arabidopsis thaliana WEE1 kinase has been cloned and tyrosine phosphorylation of its CDKs has been demonstrated, no valid candidate for a CDC25 protein has been reported in higher plants. We identify a CDC25-related protein (Arath;CDC25) of A. thaliana, constituted by a sole catalytic domain. The protein has a tyrosine-phosphatase activity and stimulates the kinase activity of Arabidopsis CDKs. Its tertiary structure was obtained by NMR spectroscopy and confirms that Arath;CDC25 belongs structurally to the classical CDC25 superfamily with a central five-stranded beta-sheet surrounded by helices. A particular feature of the protein, however, is the presence of an additional zinc-binding loop in the C-terminal part. NMR mapping studies revealed the interaction with phosphorylated peptidic models derived from the conserved CDK loop containing the phosphothreonine-14 and phosphotyrosine-15. We conclude that despite sequence divergence, Arath;CDC25 is structurally and functionally an isoform of the CDC25 superfamily, which is conserved in yeast and in plants, including Arabidopsis and rice.
双特异性CDC25磷酸酶是细胞周期蛋白依赖性激酶（CDK）的关键正向调节因子。尽管已克隆出一种具有拮抗作用的拟南芥WEE1激酶，并证明了其CDK的酪氨酸磷酸化，但高等植物中尚未报道有有效的CDC25蛋白候选物。我们鉴定出拟南芥中一种与CDC25相关的蛋白（Arath;CDC25），它由单一催化结构域组成。该蛋白具有酪氨酸磷酸酶活性，并能刺激拟南芥CDK的激酶活性。其三级结构通过核磁共振光谱获得，证实Arath;CDC25在结构上属于经典的CDC25超家族，中央有一个由螺旋包围的五链β-折叠。然而，该蛋白的一个特殊特征是在C末端部分存在一个额外的锌结合环。核磁共振图谱研究揭示了它与源自包含磷酸苏氨酸-14和磷酸酪氨酸-15的保守CDK环的磷酸化肽模型的相互作用。我们得出结论，尽管存在序列差异，但Arath;CDC25在结构和功能上是CDC25超家族的一个异构体，在酵母和包括拟南芥和水稻在内的植物中是保守的。
