Crystal structure of the Rac activator, Asef, reveals its autoinhibitory mechanism
Crystal structure of the Rac activator, Asef, reveals its autoinhibitory mechanism
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DOI：
10.1074/jbc.c600234200
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发表时间：
2007-02-16
影响因子：
4.8
通讯作者：
Yokoyama, Shigeyuki
中科院分区：
文献类型：
--
作者：
Murayama, Kazutaka;Shirouzu, Mikako;Yokoyama, Shigeyuki
Rac特异性鸟嘌呤核苷酸交换因子（GEF）Asef通过与肿瘤抑制基因腺瘤性结肠息肉病突变体结合而激活，该突变体见于散发性和家族性结直肠肿瘤。这种激活的Asef参与结直肠肿瘤细胞的迁移。Rho家族GTP酶的GEF含有Dbl同源（DH）结构域和普列克底物蛋白同源（PH）结构域。当Asef处于静息状态时，DH-PH模块的GEF活性被未鉴定的机制分子内抑制。除了DH-PH模块之外，Asef还具有Src同源性3（SH 3）结构域。在本研究中，Asef的三维结构在其自抑制状态下得到解决。晶体结构显示SH 3结构域分子内结合到DH结构域，从而阻断Rac结合位点。此外，RT-环和C-末端区域的SH 3结构域与DH结构域相互作用的方式完全不同于那些典型的结合到聚脯氨酸肽基序。这些结果表明，由SH 3结构域的RAC结合位点的封闭是必不可少的Asef自抑制。这可能是其他蛋白质中的一种常见机制，这些蛋白质具有与DH-PH模块相邻的SH 3结构域。
The Rac-specific guanine nucleotide exchange factor (GEF) Asef is activated by binding to the tumor suppressor adenomatous polyposis coli mutant, which is found in sporadic and familial colorectal tumors. This activated Asef is involved in the migration of colorectal tumor cells. The GEFs for Rho family GTPases contain the Dbl homology (DH) domain and the pleckstrin homology (PH) domain. When Asef is in the resting state, the GEF activity of the DH-PH module is intramolecularly inhibited by an unidentified mechanism. Asef has a Src homology 3 (SH3) domain in addition to the DH-PH module. In the present study, the three-dimensional structure of Asef was solved in its autoinhibited state. The crystal structure revealed that the SH3 domain binds intramolecularly to the DH domain, thus blocking the Rac-binding site. Furthermore, the RT-loop and the C-terminal region of the SH3 domain interact with the DH domain in a manner completely different from those for the canonical binding to a polyproline-peptide motif. These results demonstrate that the blocking of the Rac-binding site by the SH3 domain is essential for Asef autoinhibition. This may be a common mechanism in other proteins that possess an SH3 domain adjacent to a DH-PH module.