Huang Zhiwei, Sutton Sarah E, Wallenfang Adam J, Orchard Robert C, Wu Xiaojing, Feng Yingcai, Chai Jijie, Alto Neal M
National Institute of Biological Sciences, Zhong Guan Cun Life Science Park, Beijing, China.
Nat Struct Mol Biol. 2009 Aug;16(8):853-60. doi: 10.1038/nsmb.1647. Epub 2009 Jul 20.
The Escherichia coli type III effector Map belongs to a large family of bacterial virulence factors that activate host Rho GTPase signaling pathways through an unknown molecular mechanism. Here we report direct evidence that Map functions as a potent and selective guanine-nucleotide exchange factor (GEF) for Cdc42. The 2.3-A structure of the Map-Cdc42 complex revealed that Map mimics the GEF strategy of the mammalian Dbl family but has a three-dimensional architecture that is nearly identical to the bacterial GEF Salmonella spp. SopE. A comparative analysis between human and bacterial GEFs revealed a previously uncharacterized pairing mechanism between Map and the variable beta2-3 interswitch region of Cdc42. We propose a GTPase selection model that is experimentally validated by the preferential activation Rac1 and RhoA by the Shigella spp. effectors IpgB1 and IpgB2, respectively. These results significantly expand the repertoire of bacterial GEF mimics and unify a GEF selection mechanism for host GTPase substrates.
大肠杆菌III型效应蛋白Map属于一大类细菌毒力因子，它们通过未知分子机制激活宿主Rho GTPase信号通路。在此，我们报告直接证据表明，Map作为Cdc42的一种强效且选择性的鸟嘌呤核苷酸交换因子（GEF）发挥作用。Map-Cdc42复合物的2.3埃结构显示，Map模仿了哺乳动物Dbl家族的GEF策略，但具有与细菌GEF沙门氏菌属SopE几乎相同的三维结构。人和细菌GEF之间的比较分析揭示了Map与Cdc42可变的β2-3开关间区域之间一种此前未被表征的配对机制。我们提出了一种GTPase选择模型，志贺氏菌属效应蛋白IpgB1和IpgB2分别对Rac1和RhoA的优先激活对该模型进行了实验验证。这些结果显著扩展了细菌GEF模拟物的种类，并统一了针对宿主GTPase底物的GEF选择机制。
