Qiu M, Hua S, Agrawal M, Li G, Cai J, Chan E, Zhou H, Luo Y, Liu M
Department of Anatomical Sciences and Neurobiology, School of Medicine, University of Louisville, Louisville, Kentucky, 40202, USA.
Biochem Biophys Res Commun. 1998 Dec 18;253(2):443-7. doi: 10.1006/bbrc.1998.9795.
The SH2- and SH3-containing adaptor molecules serve to recruit cytosolic signal-transducing molecules to the activated receptor tyrosine kinases. In this study, we report the molecular cloning of a novel adaptor-like protein, Grap-2 (Grb-2 related adaptor protein 2), using the multisubstrate docking protein Gab-1 as bait in the yeast two-hybrid system. Sequence analysis revealed that Grap-2 contains a SH3-SH2-SH3 structure that has a high degree of sequence homology to those of the Grb-2 and Grap adaptor molecules. However, unlike in Grap and Grb-2, the SH2 and the C-terminal SH3 domains of Grap-2 are separated by a 120-amino-acid glutamine-rich sequence that shows no apparent homology to any known molecule or structural motif. The C-terminal SH3 domain of Grap-2 alone is sufficient to bind to Gab-1. Furthermore, Northern blot analysis demonstrated that Grap-2 has two major transcripts of 1.4 and 4.0 kb that can only be detected in tissues rich in leukocytes and in two leukemia cell lines. This highly restricted pattern of expression suggests that Grap-2 may participate in leukocyte-specific protein tyrosine kinase signaling.
含SH2和SH3结构域的衔接分子可将胞质信号转导分子募集到活化的受体酪氨酸激酶上。在本研究中，我们利用多底物对接蛋白Gab-1作为诱饵，在酵母双杂交系统中报告了一种新型衔接蛋白样蛋白Grap-2（Grb-2相关衔接蛋白2）的分子克隆。序列分析显示，Grap-2含有一个SH3-SH2-SH3结构，与Grb-2和Grap衔接分子的结构具有高度的序列同源性。然而，与Grap和Grb-2不同的是，Grap-2的SH2结构域和C端SH3结构域被一个富含120个氨基酸的谷氨酰胺序列隔开，该序列与任何已知分子或结构基序均无明显同源性。单独的Grap-2的C端SH3结构域就足以与Gab-1结合。此外，Northern印迹分析表明，Grap-2有1.4 kb和4.0 kb两种主要转录本，仅在富含白细胞的组织和两种白血病细胞系中可检测到。这种高度受限的表达模式表明，Grap-2可能参与白细胞特异性蛋白酪氨酸激酶信号传导。
