Structure-based analysis of the guanine nucleotide exchange factor SmgGDS reveals armadillo-repeat motifs and key regions for activity and GTPase binding
Structure-based analysis of the guanine nucleotide exchange factor SmgGDS reveals armadillo-repeat motifs and key regions for activity and GTPase binding
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DOI：
10.1074/jbc.m117.792556
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发表时间：
2017-08-11
影响因子：
4.8
通讯作者：
Shimizu, Toshiyuki
中科院分区：
文献类型：
--
作者：
Shimizu, Hikaru;Toma-Fukai, Sachiko;Shimizu, Toshiyuki
小GTP酶是具有关键生物学作用的分子开关，并且由GTP酶激活蛋白和鸟嘌呤核苷酸交换因子（GEF）控制。Smg GDP解离刺激物（SmgGDS）蛋白作为RhoA和RhoC小GTP酶的GEF发挥功能。SmgGDS具有多种调节作用，包括小GTP酶运输和定位以及作为分子伴侣，并与许多具有多碱基区域的小GTP酶相互作用。两种SmgGDS剪接变体SmgGDS-558和SmgGDS-607在GEF活性和对RhoA的结合亲和力方面存在差异，这取决于脂化状态，但这些差异的原因尚不清楚。在这里，我们确定了SmgGDS-558的晶体结构，揭示了一个折叠包含串联拷贝的犰狳重复不存在于其他GEF。我们还观察到SmgGDS具有不同的带正电荷和带负电荷的区域，这两者在结合RhoA和GEF活性中起关键作用。这是第一个报告，展示了SmgGDS的分子功能和原子结构之间的关系。我们的研究结果表明，两个SmgGDS异构体不同的GTdR结合和GEF活性，取决于脂质化状态，从而提供有用的信息SmgGDS在细胞中的细胞功能。
Small GTPases are molecular switches that have critical biological roles and are controlled by GTPase-activating proteins and guanine nucleotide exchange factors (GEFs). The smg GDP dissociation stimulator (SmgGDS) protein functions as a GEF for the RhoA and RhoC small GTPases. SmgGDS has various regulatory roles, including small GTPase trafficking and localization and as a molecular chaperone, and interacts with many small GTPases possessing polybasic regions. Two SmgGDS splice variants, SmgGDS-558 and SmgGDS-607, differ in GEF activity and binding affinity for RhoA depending on the lipidation state, but the reasons for these differences are unclear. Here we determined the crystal structure of SmgGDS-558, revealing a fold containing tandem copies of armadillo repeats not present in other GEFs. We also observed that SmgGDS harbors distinct positively and negatively charged regions, both of which play critical roles in binding to RhoA and GEF activity. This is the first report demonstrating a relationship between the molecular function and atomic structure of SmgGDS. Our findings indicate that the two SmgGDS isoforms differ in GTPase binding and GEF activity, depending on the lipidation state, thus providing useful information about the cellular functions of SmgGDS in cells.