Molecular cloning of a cDNA encoding a phosphoprotein, Efs, which contains a Src homology 3 domain and associates with Fyn.
Molecular cloning of a cDNA encoding a phosphoprotein, Efs, which contains a Src homology 3 domain and associates with Fyn.
复制标题
编码磷蛋白 Efs 的 cDNA 的分子克隆，Efs 包含 Src 同源 3 结构域并与 Fyn 相关。
作者：
M. Ishino;T. Ohba;Hiroko Sasaki;Terukatsu Sasaki
Src 同源 2 和 3（SH2 和 SH3）结构域通过蛋白酪氨酸激酶 (PTK) 介导细胞内信号传导中的蛋白间相互作用。我们从小鼠胚胎 cDNA 表达文库中分离出 cDNA 克隆，编码一种新的信号蛋白，我们称之为 Efs（胚胎 Fyn 相关底物）。推导出的长度为 560 个残基的氨基酸序列揭示了其氨基末端区域的一个 SH3 结构域、两个富含脯氨酸的基序（具有与 Src 家族 SH3 结合的共有序列）以及一簇可能被酪氨酸磷酸化以作为与 SH2 结构域结合的配体的 YXXP 基序。这些特征序列的结构和比对与p130Cas同源，但Efs和p130Cas是不同的蛋白质。 Efs 基因在胎盘、胚胎和大脑中的表达高于其他成人组织。用编码表位标记的 Efs 的质粒转染 COS-7 细胞，导致 83 kDa 蛋白质的表达。当与表达 Fyn 的载体共转染时，表位标记的 Efs 被过度磷酸化。在使用 PCC4 细胞裂解物进行的体外激酶测定中，Efs 在酪氨酸残基上磷酸化，并与 p59fyn 和 p62yes 共沉淀；结果表明 Efs 是这些 PTK 的生理底物。
Src homology 2 and 3 (SH2 and SH3) domains mediate protein-protein interactions in intracellular signaling by protein-tyrosine kinases (PTKs). We have isolated cDNA clones from mouse embryo cDNA expression library that encode a new signaling protein which we call Efs (Embryonal Fyn-associated Substrate). The deduced amino acid sequence of 560 residues in length revealed one SH3 domain at its amino-terminal region, two proline-rich motifs with the consensus sequences of binding to Src-family SH3s, and a cluster of YXXP motifs that are possibly tyrosine-phosphorylated to serve as ligands binding to SH2 domains. Structure and alignment of these characteristics sequences are homologous to those of p130Cas, but Efs and p130Cas are different proteins. Expression of the Efs gene was higher in placenta, embryo and brain than in other adult tissues. Transfection of COS-7 cells with a plasmid encoding an epitope-tagged Efs resulted in the expression of a 83 kDa protein. The epitope-tagged Efs was hyperphosphorylated when cotransfected with a vector expressing Fyn. In an in vitro kinase assay with the PCC4 cell lysate, Efs became phosphorylated on tyrosine residues and coprecipitated with p59fyn and p62yes; the result suggests that Efs is a physiological substrate of these PTKs.