2009年7月21日,，北京生命科學(xué)研究所柴繼杰實驗室在Nature Structural & Molecular Biology雜志在線發(fā)表題為“Structural insights into host GTPase isoform selection by a family of bacterial GEF mimics”的文章,。該研究揭示了來自一類細(xì)菌毒性因子大家族的Map通過模擬GEF活性實現(xiàn)其功能,，并提出了這類家族成員對不同GTPase的選擇模型,。生化試驗證實了該模型的預(yù)測：來自Shigella的該家族另外兩個成員IpgB1,，IpgB2分別對宿主Rac1,，RhoA具有GEF活性,。
含有WXXXE模塊的效應(yīng)蛋白屬于一類大的細(xì)菌毒性因子家族,，它們通過一種未知的GTPase信號傳遞機制調(diào)細(xì)胞骨架動態(tài)結(jié)構(gòu),。這些效應(yīng)蛋白以前被認(rèn)為是直接模擬激活的GTPases而行使其功能。但我們最近解析的沙門氏菌SifA的晶體結(jié)構(gòu)對這一觀點提出了質(zhì)疑,。該結(jié)構(gòu)顯示其C端和具有GEF活性的SopE具有相似的結(jié)構(gòu),。基于這些結(jié)構(gòu)信息,，我們推測這個家族可能具有GEF活性,。通過進一步實驗，最終鑒定出來自大腸桿菌的該家族成員Map具有對人GTPase Cdc42的GEF活性,。Map–Cdc42復(fù)合物結(jié)構(gòu)顯示Map模擬哺乳動物Dbl（GEF）的催化機制,，但卻具有和沙門氏菌GEF SopE幾乎一致的三維結(jié)構(gòu)。通過對人和細(xì)菌GEF的結(jié)構(gòu)比較分析,，發(fā)現(xiàn)Map和Cdc42內(nèi)開關(guān)區(qū)域的可變區(qū)b2-3以一種獨特的方式配對,。同時，我們提出這類家族成員對不同GTPase的選擇模型,。通過該模型發(fā)現(xiàn)來自志賀氏菌的該家族另外兩個成員IpgB1,，IpgB2分別對宿主Rac1，RhoA具有GEF活性,。這些結(jié)果擴大了人們對細(xì)菌的GEF模擬以及其對宿主GTPase底物選擇機制的認(rèn)識,。
北京生命科學(xué)研究所博士后黃志偉和德州西南醫(yī)學(xué)中心的Sarah E Sutton為本文共同第一作者。該文其他作者還有德州西南醫(yī)學(xué)中心的Adam J Wallenfang和Robert C Orchard,，以及北京生命科學(xué)研究所吳曉靜和馮英才技術(shù)員,。柴繼杰博士和德州西南醫(yī)學(xué)中心的Neal M Alto博士為本文共同通訊作者。此項研究為科技部863和北京市科委資助課題,，結(jié)構(gòu)及部分生化工作在北京生命科學(xué)研究所完成,。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature Structural & Molecular Biology 20 July 2009 | doi:10.1038/nsmb.1647
Structural insights into host GTPase isoform selection by a family of bacterial GEF mimics
Zhiwei Huang1,4, Sarah E Sutton2,4, Adam J Wallenfang2, Robert C Orchard2, Xiaojing Wu1, Yingcai Feng1, Jijie Chai1,3 & Neal M Alto2
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-? 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 2-3 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.
1 National Institute of Biological Sciences, Zhong Guan Cun Life Science Park, Beijing, China.
2 Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA.
3 Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing, China.
4 These authors contributed equally to this work.
