Key Laboratory of Resources Biology and Biotechnology in Western China, Ministry of Education, College of Life Sciences, Northwest University, Xi'an, Shaanxi, 710069, China.
State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, 200433, China.
Mol Microbiol. 2019 May;111(5):1195-1210. doi: 10.1111/mmi.14200. Epub 2019 Mar 29.
Pseudomonas aeruginosa is a major pathogen that causes serious acute and chronic infections in humans. The type III secretion system (T3SS) is an important virulence factor that plays essential roles in acute infections. However, the regulatory mechanisms of T3SS are not fully understood. In this study, we found that the deletion of cysB reduced the T3SS gene expression and swarming motility but enhanced biofilm formation. In a mouse acute pneumonia model, mutation of cysB decreased the average bacterial load compared to that of the wild-type strain. Further experiments demonstrated that CysB contributed to the reduced T3SS gene expression and bacterial pathogenesis by directly regulating the sensor kinase RetS. We also performed crystallographic studies of PaCysB. The overall fold of PaCysB NTD domain is similar to other LysR superfamily proteins and structural superposition revealed one possible DNA-binding model for PaCysB. Structural comparison also revealed great flexibility of the PaCysB RD domain, which may play an important role in bending and transcriptional regulation of target DNA. Taken together, these results expand our current understanding of the complex regulatory networks of T3SS and RetS pathways. The crystal structure of CysB provides new insights for studying the function of its homologs in other bacterial species.
铜绿假单胞菌是一种主要的病原体，可导致人类严重的急性和慢性感染。III 型分泌系统（T3SS）是一种重要的毒力因子，在急性感染中起着至关重要的作用。然而，T3SS 的调控机制尚未完全阐明。在本研究中，我们发现 cysB 的缺失减少了 T3SS 基因的表达和群集运动，但增强了生物膜的形成。在小鼠急性肺炎模型中，与野生型菌株相比，cysB 的突变导致平均细菌负荷减少。进一步的实验表明，CysB 通过直接调节传感器激酶 RetS 来减少 T3SS 基因的表达和细菌发病机制。我们还进行了 PaCysB 的晶体学研究。PaCysB NTD 结构域的整体折叠与其他 LysR 超家族蛋白相似，结构叠加揭示了 PaCysB 的一个可能的 DNA 结合模型。结构比较还揭示了 PaCysB RD 结构域的极大灵活性，这可能在弯曲和靶 DNA 的转录调控中发挥重要作用。总之，这些结果扩展了我们对 T3SS 和 RetS 途径复杂调控网络的现有认识。CysB 的晶体结构为研究其在其他细菌物种中的同源物的功能提供了新的见解。
