Tschauner Karolin, Hörnschemeyer Patrick, Müller Volker Steffen, Hunke Sabine
University of Osnabrück, FB5, Molecular Microbiology, Osnabrück, Germany.
Humboldt University Berlin, Department of Biology, Bacterial Physiology, Berlin, Germany.
PLoS One. 2014 Sep 10;9(9):e107383. doi: 10.1371/journal.pone.0107383. eCollection 2014.
Two-component systems, consisting of an inner membrane sensor kinase and a cytosolic response regulator, allow bacteria to respond to changes in the environment. Some two-component systems are additionally orchestrated by an accessory protein that integrates additional signals. It is assumed that spatial and temporal interaction between an accessory protein and a sensor kinase modifies the activity of a two-component system. However, for most accessory proteins located in the bacterial envelope the mechanistic details remain unclear. Here, we analyzed the interaction between the periplasmic accessory protein CpxP and the sensor kinase CpxA in Escherichia coli in dependency of three specific stimuli. The Cpx two-component system responds to envelope stress and plays a pivotal role for the quality control of multisubunit envelope structures, including type three secretion systems and pili of different pathogens. In unstressed cells, CpxP shuts off the Cpx response by a yet unknown mechanism. We show for the first time the physical interaction between CpxP and CpxA in unstressed cells using bacterial two-hybrid system and membrane-Strep-tagged protein interaction experiments. In addition, we demonstrate that a high salt concentration and the misfolded pilus subunit PapE displace CpxP from the sensor kinase CpxA in vivo. Overall, this study provides clear evidence that CpxP modulates the activity of the Cpx system by dynamic interaction with CpxA in response to specific stresses.
双组分系统由内膜传感器激酶和胞质反应调节因子组成，使细菌能够对环境变化做出反应。一些双组分系统还由整合额外信号的辅助蛋白进行协调。据推测，辅助蛋白与传感器激酶之间的时空相互作用会改变双组分系统的活性。然而，对于大多数位于细菌包膜中的辅助蛋白，其作用机制的细节仍不清楚。在这里，我们分析了大肠杆菌中周质辅助蛋白CpxP与传感器激酶CpxA之间在三种特定刺激下的相互作用。Cpx双组分系统对包膜应激做出反应，在多亚基包膜结构（包括不同病原体的三型分泌系统和菌毛）的质量控制中起关键作用。在未受应激的细胞中，CpxP通过一种未知机制关闭Cpx反应。我们首次使用细菌双杂交系统和膜链霉亲和标签蛋白相互作用实验，展示了未受应激细胞中CpxP与CpxA之间的物理相互作用。此外，我们证明高盐浓度和错误折叠的菌毛亚基PapE在体内会将CpxP从传感器激酶CpxA上置换下来。总体而言，这项研究提供了明确的证据，表明CpxP通过在特定应激下与CpxA的动态相互作用来调节Cpx系统的活性。
