Binding of Rac1, Rnd1, and RhoD to a novel Rho GTPase interaction motif destabilizes dimerization of the plexin-B1 effector domain
Binding of Rac1, Rnd1, and RhoD to a novel Rho GTPase interaction motif destabilizes dimerization of the plexin-B1 effector domain
复制标题
DOI：
10.1074/jbc.m703800200
复制
发表时间：
2007-12-21
影响因子：
4.8
通讯作者：
Buck, Matthias
中科院分区：
文献类型：
--
作者：
Tong, Yufeng;Chugha, Preeti;Buck, Matthias
丛状蛋白是第一个已知的直接与小GTP酶相互作用的跨膜受体。在与某些Rho家族GTP酶结合时，该受体调节肌动蛋白细胞骨架的重塑，并改变细胞的运动，以响应信号素引导信号。在联合溶液核磁共振波谱和X射线结晶学研究中，我们表征了Plexin-B1的120个残基的胞质独立折叠结构域，它直接结合了Rho家族的三个GTP酶，rac1，RND1和Rhod。核磁共振数据表明，令人惊讶的是，Plexin-B1的Cdc42/RAC相互作用结合样基序没有参与这种相互作用。相反，所有这三种GTP酶都与相同的区域、β-链3和4以及丛蛋白结构域的一小段α-螺旋相互作用。2.0埃分辨率的X射线结构表明，这些片段是通过泛素样折叠的三级结构结合在一起的。在晶体中，蛋白质通过四链反平行的β-折叠以C2对称性二聚化，该折叠外部通过单体之间的长环形成。该区域与核磁共振鉴定的GTP酶结合基序相邻。通过结合三种GTP酶中的任何一种来破坏溶液中二聚体的稳定性，表明了一种涉及双向信号转导的受体调节模型。该模型暗示了GTPase-丛蛋白相互作用的多功能作用，包括构象变化和信号机制中活性受体的定位。
Plexins are the first known transmembrane receptors that interact directly with small GTPases. On binding to certain Rho family GTPases, the receptor regulates the remodeling of the actin cytoskeleton and alters cell movement in response to semaphorin guidance cues. In a joint solution NMR spectroscopy and x-ray crystallographic study, we characterize a 120-residue cytoplasmic independent folding domain of plexin-B1 that directly binds three Rho family GTPases, Rac1, Rnd1, and RhoD. The NMR data show that, surprisingly, the Cdc42/Rac interactive binding-like motif of plexin-B1 is not involved in this interaction. Instead, all three GTPases interact with the same region, beta-strands 3 and 4 and a short alpha-helical segment of the plexin domain. The 2.0 angstrom resolution x-ray structure shows that these segments are brought together by the tertiary structure of the ubiquitin-like fold. In the crystal, the protein is dimerized with C2 symmetry through a four-stranded antiparallel beta-sheet that is formed outside the fold by a long loop between the monomers. This region is adjacent to the GTPase binding motifs identified by NMR. Destabilization of the dimer in solution by binding of any one of the three GTPases suggests a model for receptor regulation that involves bidirectional signaling. The model implies a multifunctional role for the GTPase-plexin interaction that includes conformational change and a localization of active receptors in the signaling mechanism.