Hu K Q, Settleman J
Massachusetts General Hospital Cancer Center and Harvard Medical School, Charlestown 02129, USA.
EMBO J. 1997 Feb 3;16(3):473-83. doi: 10.1093/emboj/16.3.473.
Many cellular signaling proteins contain SH3 (Src homology 3) domains that mediate protein interactions via specific proline-containing peptides. Unlike SH2 domains, whose interactions with tyrosine-containing peptides are promoted by phosphorylation of the SH2 binding site, the regulatory mechanism for SH3 interactions is unclear. p120 RasGAP (GTPase-activating protein), which contains an SH3 domain flanked by two SH2 domains, forms an abundant SH2-mediated complex with p190 RhoGAP in cells expressing activated tyrosine kinases. We have identified two closely linked tyrosine-containing peptides in p190 that bind simultaneously to the RasGAP SH2 domains upon p190 phosphorylation. This interaction is expected to bring the two SH2 domains into close proximity. Consequently, RasGAP undergoes a conformational change that results in a 100-fold increase in the accessibility of the target binding surface of its SH3 domain. These results indicate that the tandem arrangement of SH2 and SH3 domains found in a variety of cellular signaling proteins can provide a conformational mechanism for regulating SH3-dependent interactions through tyrosine phosphorylation. In addition, it appears that the role of p190 in the RasGAP signaling complex is to promote additional protein interactions with RasGAP via its SH3 domain.
许多细胞信号蛋白含有SH3（Src同源结构域3）结构域，该结构域通过特定的含脯氨酸肽介导蛋白质相互作用。与SH2结构域不同，SH2结构域与含酪氨酸肽的相互作用是由SH2结合位点的磷酸化促进的，而SH3相互作用的调节机制尚不清楚。p120 RasGAP（GTP酶激活蛋白）含有一个位于两个SH2结构域之间的SH3结构域，在表达活化酪氨酸激酶的细胞中，它与p190 RhoGAP形成丰富的SH2介导的复合物。我们在p190中鉴定出两个紧密相连的含酪氨酸肽，在p190磷酸化后，它们同时与RasGAP的SH2结构域结合。这种相互作用预计会使两个SH2结构域紧密靠近。因此，RasGAP发生构象变化，导致其SH3结构域靶标结合表面的可及性增加100倍。这些结果表明，在多种细胞信号蛋白中发现的SH2和SH3结构域的串联排列可以提供一种通过酪氨酸磷酸化调节SH3依赖性相互作用的构象机制。此外，p190在RasGAP信号复合物中的作用似乎是通过其SH3结构域促进与RasGAP的额外蛋白质相互作用。
