Structure of Shigella IpgB2 in Complex with Human RhoA IMPLICATIONS FOR THE MECHANISM OF BACTERIAL GUANINE NUCLEOTIDE EXCHANGE FACTOR MIMICRY
Structure of Shigella IpgB2 in Complex with Human RhoA IMPLICATIONS FOR THE MECHANISM OF BACTERIAL GUANINE NUCLEOTIDE EXCHANGE FACTOR MIMICRY
复制标题
DOI：
10.1074/jbc.m110.107953
复制
发表时间：
2010-05-28
影响因子：
4.8
通讯作者：
Heinz, Dirk W.
中科院分区：
文献类型：
--
作者：
Klink, Bjoern U.;Barden, Stephan;Heinz, Dirk W.
细菌致病机制中的一个共同主题是通过靶向细胞骨架来操纵真核细胞。在大多数情况下，这是通过修饰肌动蛋白，或间接通过激活控制肌动蛋白动力学的关键调节因子，如Rho-GTP酶来实现的。一组新的细菌毒力因子被称为WXXXE家族已经出现作为这些GTP酶的鸟嘌呤核苷酸交换因子（GEF）。然而，核苷酸交换的确切机制仍不清楚。在这里，我们报告的WXXXE-蛋白IpgB 2从志贺氏菌及其与人类RhoA的复合物的结构。我们毫不含糊地确定IpgB 2作为一种细菌RhoA-GEF和解剖GDP释放的分子机制，GTP结合的必要先决条件。我们的观察发现，IpgB 2诱导RhoA模仿DbI的构象变化，但不是DOCK家族GEF。我们还表明，GDP.Mg2+复合物的解离之前的金属离子的置换的α-磷酸的核苷酸，降低其亲和力的GTdR。这些数据完善了我们的理解不仅WXXXE GEFs的行动模式，但也哺乳动物GEFs的DH/PH家庭。
A common theme in bacterial pathogenesis is the manipulation of eukaryotic cells by targeting the cytoskeleton. This is in most cases achieved either by modifying actin, or indirectly via activation of key regulators controlling actin dynamics such as Rho-GTPases. A novel group of bacterial virulence factors termed the WXXXE family has emerged as guanine nucleotide exchange factors (GEFs) for these GTPases. The precise mechanism of nucleotide exchange, however, has remained unclear. Here we report the structure of the WXXXE-protein IpgB2 from Shigella flexneri and its complex with human RhoA. We unambiguously identify IpgB2 as a bacterial RhoA-GEF and dissect the molecular mechanism of GDP release, an essential prerequisite for GTP binding. Our observations uncover that IpgB2 induces conformational changes on RhoA mimicking DbI-but not DOCK family GEFs. We also show that dissociation of the GDP.Mg2+ complex is preceded by the displacement of the metal ion to the alpha-phosphate of the nucleotide, diminishing its affinity to the GTPase. These data refine our understanding of the mode of action not only of WXXXE GEFs but also of mammalian GEFs of the DH/PH family.