血管内皮生长因子受体1酪氨酸激酶的克隆、表达和功能

血管内皮生长因子受体 1(Flt 1)在血管生成过程中起着重要的作用。Flt 1胞内域的酪氨酸激酶直接参与了VEGF与Flt 1结合后的胞内信号转导途径。在原核系统中表达得到具有酶活性的Flt 1酪氨酸激酶融合蛋白 ,并进行了初步的性质研究。利用逆转录PCR技术从人肝癌组织总RNA中得到Flt 1酪氨酸激酶区的cDNA ,将其克隆到表达载体质粒 pGEX KG中 ,并在大肠杆菌BL2 1(DE3) pLysS中表达、纯化 ,得到可溶的Flt 1酪氨酸激酶融合蛋白 (GST F)。虽然GST F不包含目前已知的磷酸化位点 ,但研究表明GST F能够进行自磷酸化反应 ,并且其活性需要镁离子或锰离子的参与。同时发现GST F能够磷酸化合成底物 polyE4Y ,而不能作用于MBP和Src相关肽。底物磷酸化时最适的镁离子和锰离子浓度分别为 15mmol/L和 0 .5mmol/L。GST F为寻找抗肿瘤药物提供了一个有效工具

Cloning, Expression and Characterization of Human Vascular Endothelial Growth Factor Receptor 1 Tyrosine Kinase

Vascular endothelial growth factor receptor 1 (Flt1) plays an important role in angiogenesis. It was hypothesized that, upon binding to VEGF, Flt1 tyrosine kinase underwent dimerization and initiated the signal transduction in VEGF/VEGF receptor system. In this report, a soluble active Flt1 tyrosine kinase domain expressed in E.coli was obtained, and its properties were partly characterized. The cDNA of Flt1 tyrosine kinase domain was obtained from the total RNA extracted from human liver cancer tissues by using RT-PCR, and was cloned to vector pGEX-KG. A soluble active GST-fusion protein of Flt1 tyrosine kinase domain (GST-F) was obtained from E.coli BL21 (DE3) pLysS. Athough it was reported that GST-F contains no phosphorylation site, it did autophosphorylate in vitro. Mg 2 and Mn 2 were essential for the activity. It was also found that GST-F phosphorylated a synthesized substrate PolyE4Y, but not MBP and Src-related-peptide. The optimal Mg 2 and Mn 2 concentration for polyE4Y phosphorylation was 15 mmol/L and 0.5 mmol/L, respectively. This work is helpful for developing the new anti-cancer drugs.