Structural Studies of the Pseudokinase Domain of Jak2.

描述（由申请人提供）：Janus激酶（Jaks）是非受体蛋白酪氨酸激酶家族的成员，是免疫系统细胞和造血细胞信号通路的关键组成部分。Jaks与细胞因子受体的细胞质结构域有关，在细胞因子介导的受体二聚化过程中，酪氨酸残基发生反式自磷酸化，从而刺激其酪氨酸激酶活性。激活的Jaks使stat（转录的信号转导和激活因子）磷酸化，后者转运到细胞核并充当转录激活因子。在哺乳动物中，Jak家族有4个成员（Jak1-3和Tyk2），它们具有4个共同的结构域：n端FERM结构域、sh2样结构域、假激酶结构域和酪氨酸激酶结构域。大量的生化数据，以及导致骨髓增生性疾病/癌症的功能获得性突变，都暗示Jaks的假激酶结构域对于维持低基础水平的酪氨酸激酶活性至关重要。本研究的目的是了解假激酶结构域负调控Jak2酪氨酸激酶活性的结构/分子机制。为了实现这一目标，x射线晶体学将被用来确定假激酶结构域和串联假激酶和酪氨酸激酶结构域的三维结构。

DESCRIPTION (provided by applicant): Janus kinases (Jaks), members of the non-receptor protein tyrosine kinase family, are key components of signaling pathways in cells of the immune system and in hematopoietic cells. Jaks are associated with the cytoplasmic domains of cytokine receptors and, upon cytokine-mediated receptor dimerization, undergo trans- autophosphorylation on tyrosine residues, which stimulates their tyrosine kinase activity. Activated Jaks phosphorylate STATs (signal transducers and activators of transcription), which translocate to the nucleus and serve as transcriptional activators. There are four mammalian members of the Jak family (Jak1-3 and Tyk2) which possess four domains in common: an N-terminal FERM domain, an SH2-like domain, a pseudokinase domain, and a tyrosine kinase domain. Extensive biochemical data, as well as gain-of-function mutations that cause myeloproliferative diseases/cancers, have implicated the pseudokinase domain of Jaks as crucial for maintaining a low basal level of tyrosine kinase activity. The goal of this proposal is to understand the structural/molecular mechanisms by which the pseudokinase domain negatively regulates the tyrosine kinase activity of Jak2. To achieve this goal, x-ray crystallography will be employed to determine the three-dimensional structures of the pseudokinase domain and the tandem pseudokinase and tyrosine kinase domains.