Solution Structure, Backbone Dynamics, and Interaction with Cdc42 of Salmonella Guanine Nucleotide Exchange Factor SopE2
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- 作者：Christopher Williams ; Edouard E. Galyov ; and Stefan Bagby
- 刊名：Biochemistry
- 出版年：2004
- 出版时间：September 28, 2004
- 年：2004
- 卷：43
- 期：38
- 页码：11998 - 12008
- 全文大小：550K
- 年卷期：v.43,no.38(September 28, 2004)
- ISSN：1520-4995
文摘
SopE and SopE2 are delivered by the Salmonella type III secretion system into eukaryoticcells to promote cell invasion. SopE and SopE2 are potent guanine nucleotide exchange factors (GEFs)for Rho GTPases Cdc42 and Rac1 and constitute a novel class of Rho GEFs. Although the sequence ofSopE-like GEFs is not at all homologous to those of the Dbl homology domain-containing eukaryoticGEFs, the mechanism of nucleotide release seems to have significant similarities. We have determinedthe solution structure of the catalytic domain (residues 69-240) of SopE2, showing that SopE269-240comprises two three-helix bundles (
145 and 236) arranged in a 
shape. Compared to the crystalstructure of SopE78-240 in complex with Cdc42, SopE269-240 exhibits a less open shape due to movementof SopE78-240 helices 2 and 5 to accommodate binding to the Cdc42 switch regions. In an NMR titrationto investigate the SopE269-240-Cdc42 interaction, the SopE269-240 residues affected by binding Cdc42were very similar to the SopE78-240 residues that contact Cdc42 in the SopE78-240-Cdc42 complex. Analysisof the backbone 15N dynamics of SopE269-240 revealed flexibility in residues that link the two three-helixbundles, including the 3-4 linker that incorporates a 
-hairpin and the catalytic loop, and the 5-6loop, and flexibility in residues involved in interaction with Cdc42. Together, these observations provideexperimental evidence of a previously proposed mechanism of GEF-mediated nucleotide exchange basedon the Rac1-Tiam1 complex structure, with SopE/E2 flexibility, particularly in the interbundle loops,enabling conformational rearrangements of the nucleotide binding region of Cdc42 through an inducedfit type of binding. Such flexibility in SopE/E2 may also facilitate interaction through adaptive bindingwith alternative target proteins such as Rab5, allograft inflammatory factor 1, and apolipoprotein A-1.
145 and 236) arranged in a shape. Compared to the crystalstructure of SopE78-240 in complex with Cdc42, SopE269-240 exhibits a less open shape due to movementof SopE78-240 helices 2 and 5 to accommodate binding to the Cdc42 switch regions. In an NMR titrationto investigate the SopE269-240-Cdc42 interaction, the SopE269-240 residues affected by binding Cdc42were very similar to the SopE78-240 residues that contact Cdc42 in the SopE78-240-Cdc42 complex. Analysisof the backbone 15N dynamics of SopE269-240 revealed flexibility in residues that link the two three-helixbundles, including the 3-4 linker that incorporates a -hairpin and the catalytic loop, and the 5-6loop, and flexibility in residues involved in interaction with Cdc42. Together, these observations provideexperimental evidence of a previously proposed mechanism of GEF-mediated nucleotide exchange basedon the Rac1-Tiam1 complex structure, with SopE/E2 flexibility, particularly in the interbundle loops,enabling conformational rearrangements of the nucleotide binding region of Cdc42 through an inducedfit type of binding. Such flexibility in SopE/E2 may also facilitate interaction through adaptive bindingwith alternative target proteins such as Rab5, allograft inflammatory factor 1, and apolipoprotein A-1.