Program in Applied Biological Sciences, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, Bangkok, Thailand.
Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, Thailand.
Microbiology (Reading). 2019 Oct;165(10):1117-1134. doi: 10.1099/mic.0.000838.
The ActSR two-component regulatory system is a member of a homologous group of global redox-responsive regulatory systems that adjust the expression of energy-consuming and energy-supplying metabolic pathways in order to maintain cellular redox balance. In this study, the transcriptional organization of the locus was determined and the effect of system inactivation on stress resistance was investigated. It was found that is transcribed as a monocistronic mRNA and is transcribed along with as a bicistronic mRNA, while is also transcribed as a monocistronic message. Each message is initiated from a separate promoter. Inactivation of resulted in decreased resistance to membrane stress (sodium dodecyl sulfate), acid stress (pH 5.5), iron starvation (bipyridyl) and iron excess (FeCl), and antibiotic stress (tetracycline and ciprofloxacin). Resistance to oxidative stress in the form of organic peroxide (cumene hydroperoxide) increased, while resistance to inorganic peroxide (HO) decreased. An insertion mutant displayed reduced catalase activity, even though transcription of and remained unchanged. Complementation of the inactivation mutant with plasmid-encoded or overexpression of , encoding ferrochelatase, restored wild-type catalase activity and HO resistance levels. Gel mobility shift and promoter fusion results indicated that ActR is a positive regulator of that binds directly to the promoter region. Thus, inactivation of the ActSR system affects resistance to multiple stresses, including reduced resistance to HO resulting from a reduction in catalase activity due to reduced expression of .
ActSR 双组分调控系统是全球氧化还原响应调控系统同源群的成员之一，它调节能量消耗和能量供应代谢途径的表达，以维持细胞氧化还原平衡。在本研究中，确定了 基因座的转录组织，并研究了 系统失活对抵抗应激的影响。结果发现， 作为单顺反子 mRNA 转录，而 与 一起作为双顺反子 mRNA 转录，而 也作为单顺反子 mRNA 转录。每个消息都从一个单独的启动子开始。 失活导致对膜应激（十二烷基硫酸钠）、酸应激（pH5.5）、铁饥饿（联吡啶）和铁过量（FeCl）以及抗生素应激（四环素和环丙沙星）的抵抗力降低。以有机过氧化物（枯烯过氧化氢）形式的氧化应激抗性增加，而无机过氧化物（HO）的抗性降低。 插入突变体显示出降低的过氧化氢酶活性，尽管 和 的转录仍然不变。用质粒编码的 或过表达编码亚铁螯合酶的 互补 失活突变体，恢复了野生型过氧化氢酶活性和 HO 抗性水平。凝胶迁移率变动和 启动子融合结果表明，ActR 是 的正调控因子，它直接结合到 启动子区域。因此， ActSR 系统的失活会影响对多种应激的抵抗能力，包括由于过氧化氢酶活性降低导致的 HO 抵抗能力降低，这是由于 表达减少所致。
