Xu Huangwei, Xuan Guanhua, Liu Huaiwei, Liu Honglei, Xia Yongzhen, Xun Luying
State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China.
Food Safety Laboratory, College of Food Science and Engineering, Ocean University of China, Qingdao 266100, China.
Antioxidants (Basel). 2022 Aug 26;11(9):1667. doi: 10.3390/antiox11091667.
Sulfane sulfur, including organic persulfide and polysulfide, is a normal cellular component, and its level varies during growth. It is emerging as a signaling molecule in bacteria, regulating the gene regulator MarR in , MexR in , and MgrA of . They are MarR-family regulators and are often repressors for multiple antibiotic resistance genes. Here, we report that another MarR-type regulator OhrR that represses the expression of itself and a thiol peroxidase gene in PAO1 also responded to sulfane sulfur. PaOhrR formed disulfide bonds between three Cys residues within a dimer after polysulfide treatment. The modification reduced its affinity to its cognate DNA binding site. An reporter system, in which mKate was under the repression of OhrR, showed that PaOhrR derepressed its controlled gene when polysulfide was added, whereas the mutant PaOhrR with two Cys residues changed to Ser residues did not respond to polysulfide. The expression of the PaOhrR-repressed mKate was significantly increased when the cells enter the late log phase when cellular sulfane sulfur reached a maximum, but the mKate expression under the control of the PaOhrR-C9SC19S double mutant was not increased. Furthermore, the expression levels of and in PAO1 were significantly increased when cellular sulfane sulfur was high. Thus, PaOhrR senses both exogenous and intrinsic sulfane sulfur to derepress its controlled genes. The finding also suggests that sulfane sulfur may be a common inducer of the MarR-type regulators, which may confer the bacteria to resist certain stresses without being exposed to the stresses.
包括有机二硫化物和多硫化物在内的硫化氢是细胞的正常组成成分，其水平在生长过程中会发生变化。硫化氢正在成为细菌中的一种信号分子，可调节铜绿假单胞菌中的基因调节因子MarR、MexR以及MgrA。它们属于MarR家族调节因子，通常是多种抗生素抗性基因的阻遏物。在此，我们报告另一种MarR型调节因子OhrR，它在铜绿假单胞菌PAO1中可抑制自身及硫醇过氧化物酶基因的表达，该调节因子也对硫化氢有反应。多硫化物处理后，PaOhrR在二聚体内的三个半胱氨酸残基之间形成了二硫键。这种修饰降低了它与同源DNA结合位点的亲和力。一个报告系统显示，在该系统中mKate受OhrR的抑制，当加入多硫化物时，PaOhrR会解除对其控制基因的抑制，而两个半胱氨酸残基突变为丝氨酸残基的突变体PaOhrR对多硫化物没有反应。当细胞进入对数后期，细胞内硫化氢达到最大值时，受PaOhrR抑制的mKate的表达显著增加，但在PaOhrR - C9SC19S双突变体控制下的mKate表达并未增加。此外，当细胞内硫化氢含量较高时，铜绿假单胞菌PAO1中相关基因的表达水平显著增加。因此，PaOhrR可感知外源性和内源性硫化氢，以解除对其控制基因的抑制。这一发现还表明，硫化氢可能是MarR型调节因子的常见诱导物，这可能使细菌在未接触某些压力的情况下就能抵抗这些压力。
