Songyang Z, Yamanashi Y, Liu D, Baltimore D
Verna and Marrs Mclean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
J Biol Chem. 2001 Jan 26;276(4):2459-65. doi: 10.1074/jbc.M005504200. Epub 2000 Oct 19.
p62Dok, the rasGAP-binding protein, is a common target of protein-tyrosine kinases. It is one of the major tyrosine-phosphorylated molecules in v-Src-transformed cells. Dok consists of an amino-terminal Pleckstrin homology domain, a putative phosphotyrosine binding domain, and a carboxyl-terminal tail containing multiple tyrosine phosphorylation sites. The importance and function of these sequences in Dok signaling remain largely unknown. We have demonstrated here that the expression of Dok can inhibit cellular transformation by the Src tyrosine kinase. Both the phosphotyrosine binding domain and the carboxyl-terminal tail of Dok (in particular residues 336-363) are necessary for such activity. Using a combinatorial peptide library approach, we have shown that the Dok phosphotyrosine binding domain binds phosphopeptides with the consensus motif of Y/MXXNXL-phosphotyrosine. Furthermore, Dok can homodimerize through its phosphotyrosine binding domain and Tyr(146) at the amino-terminal region. Mutations of this domain or Tyr(146) that block homodimerization significantly reduce the ability of Dok to inhibit Src transformation. Our results suggest that Dok oligomerization through its multiple domains plays a critical role in Dok signaling in response to tyrosine kinase activation.
p62Dok，一种与RasGAP结合的蛋白质，是蛋白酪氨酸激酶的常见作用靶点。它是v-Src转化细胞中主要的酪氨酸磷酸化分子之一。Dok由一个氨基末端的普列克底物蛋白同源结构域、一个假定的磷酸酪氨酸结合结构域以及一个含有多个酪氨酸磷酸化位点的羧基末端尾巴组成。这些序列在Dok信号传导中的重要性和功能仍 largely未知。我们在此证明，Dok的表达可抑制Src酪氨酸激酶介导的细胞转化。Dok的磷酸酪氨酸结合结构域和羧基末端尾巴（特别是336 - 363位残基）对于这种活性是必需的。使用组合肽库方法，我们表明Dok的磷酸酪氨酸结合结构域结合具有Y/MXXNXL - 磷酸酪氨酸一致基序的磷酸肽。此外，Dok可通过其磷酸酪氨酸结合结构域和氨基末端区域的Tyr(146)进行同源二聚化。该结构域或Tyr(146)的突变若阻断同源二聚化，则会显著降低Dok抑制Src转化的能力。我们的结果表明，Dok通过其多个结构域进行寡聚化在响应酪氨酸激酶激活的Dok信号传导中起关键作用。
