Structural Studies of the Pseudokinase Domain of Jak2

Janus激酶（Jaks），非受体蛋白酪氨酸激酶家族的成员，是细胞内蛋白质的关键组分。 免疫系统细胞和造血细胞中的信号通路。Jaks与 细胞因子受体的胞质结构域，并在精氨酸介导的受体二聚化后，进行转自磷酸化 对酪氨酸残基，这刺激其酪氨酸激酶活性。激活Jaks 磷酸化STAT（信号转导和转录激活因子），其易位到细胞核， 作为转录激活因子。Jak家族有四个哺乳动物成员（Jak 1 -3和Tyk 2）。 其共有四个结构域：N-末端FERM结构域、SH 2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，以及功能获得性突变， 导致骨髓增生性疾病/癌症，已经暗示Jaks的假激酶结构域对于 维持酪氨酸激酶活性的低基础水平。本提案的目的是了解 假激酶结构域负调节酪氨酸激酶的结构/分子机制 Jak 2的活动。为了实现这一目标，X射线晶体学将被用来确定三维的 假激酶结构域和串联的假激酶和酪氨酸激酶结构域的结构。

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 transautophosphorylation 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.