Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea.
Protein Sci. 2012 Sep;21(9):1334-43. doi: 10.1002/pro.2120.
The Cpx two-component system of Gram-negative bacteria senses extracytoplasmic stresses using the histidine kinase CpxA, a membrane-bound sensor, and controls the transcription of the genes involved in stress response by the cytosolic response regulator CpxR, which is activated by the phosphorelay from CpxA. CpxP, a CpxA-associated protein, also plays an important role in the regulation of the Cpx system by inhibiting the autophosphorylation of CpxA. Although the stress signals and physiological roles of the Cpx system have been extensively studied, the lack of structural information has limited the understanding of the detailed mechanism of ligand binding and regulation of CpxA. In this study, we solved the crystal structure of the periplasmic domain of Vibrio parahaemolyticus CpxA (VpCpxA-peri) to a resolution of 2.1 Å and investigated its interaction with CpxP. VpCpxA-peri has a globular Per-ARNT-SIM (PAS) domain and a protruded C-terminal tail, which may be required for ligand sensing and CpxP binding, respectively. The direct interaction of the PAS core of VpCpxA-peri with VpCpxP was not detected by NMR, suggesting that the C-terminal tail or other factors, such as the membrane environment, are necessary for the binding of CpxA to CpxP.
革兰氏阴性菌的 Cpx 双组分系统使用膜结合传感器 CpxA 感应细胞外应激，并通过磷酸传递从 CpxA 激活的胞质响应调节剂 CpxR 控制参与应激反应的基因的转录。CpxA 相关蛋白 CpxP 也通过抑制 CpxA 的自磷酸化在 Cpx 系统的调节中发挥重要作用。尽管 Cpx 系统的应激信号和生理作用已经得到了广泛的研究，但缺乏结构信息限制了对 CpxA 配体结合和调节的详细机制的理解。在这项研究中，我们解决了副溶血性弧菌 CpxA（VpCpxA-peri）周质域的晶体结构，分辨率为 2.1Å，并研究了其与 CpxP 的相互作用。VpCpxA-peri 具有球形的 Per-ARNT-SIM（PAS）结构域和突出的 C 末端尾巴，这可能分别是配体感应和 CpxP 结合所必需的。NMR 未检测到 VpCpxA-peri 的 PAS 核心与 VpCpxP 的直接相互作用，这表明 C 末端尾巴或其他因素，如膜环境，是 CpxA 与 CpxP 结合所必需的。
