Center of Emphasis in Infectious Diseases and Department of Biomedical Sciences, Paul L. Foster School of Medicine, Texas Tech University Health Sciences Center El Paso, Texas, 79905, USA.
Sci Rep. 2017 Jun 20;7(1):3922. doi: 10.1038/s41598-017-03819-1.
Organic hydroperoxide reductase regulator (OhrR) in bacteria is a sensor for organic hydroperoxide stress and a transcriptional regulator for the enzyme organic hydroperoxide reductase (Ohr). In this study we investigated, using a GFP reporter system, whether Mycobacterium smegmatis OhrR has the ability to sense and respond to intracellular organic hydroperoxide stress. It was observed that M. smegmatis strains bearing the pohr-gfpuv fusion construct were able to express GFP only in the absence of an intact ohrR gene, but not in its presence. However, GFP expression in the strain bearing pohr-gfpuv with an intact ohrR gene could be induced by organic hydroperoxides in vitro and in the intracellular environment upon ingestion of the bacteria by macrophages; indicating that OhrR responds not only to in vitro but also to intracellular organic hydroperoxide stress. Further, the intracellular expression of pohr driven GFP in this strain could be abolished by replacing the intact ohrR gene with a mutant ohrR gene modified for N-terminal Cysteine (Cys) residue, suggesting that OhrR senses intracellular organic hydroperoxides through Cys residue. This is the first report demonstrating the ability of OhrR to sense intracellular organic hydroperoxides.
细菌中的有机氢过氧化物还原酶调节因子 (OhrR) 是有机氢过氧化物应激的传感器，也是有机氢过氧化物还原酶 (Ohr) 的转录调节因子。在这项研究中，我们使用 GFP 报告系统研究了分枝杆菌 OhrR 是否具有感知和应对细胞内有机氢过氧化物应激的能力。结果观察到，带有 pohr-gfpuv 融合构建体的耻垢分枝杆菌菌株仅在不存在完整 ohrR 基因的情况下才能表达 GFP，但在其存在的情况下则不能。然而，带有完整 ohrR 基因的 pohr-gfpuv 菌株中的 GFP 表达可以在体外和巨噬细胞摄取细菌后的细胞内环境中被有机过氧化物诱导；表明 OhrR 不仅对体外，而且对细胞内有机氢过氧化物应激有反应。此外，通过用修饰的 N 端半胱氨酸 (Cys) 残基的突变 ohrR 基因替换完整的 ohrR 基因，可以消除该菌株中由 pohr 驱动的 GFP 的细胞内表达，表明 OhrR 通过 Cys 残基感知细胞内有机氢过氧化物。这是首次报道 OhrR 能够感知细胞内有机氢过氧化物的能力。
