Characterization of the HOCl-specific Transcription Factor HypT in Salmonella enterica serovar Typhimurium

Salmonella;HypT;HOCl;iron acquisition;methionine oxidation;630

농업생명과학대학 농생명공학부 ;

University:서울대학교 대학원

关键词: Salmonella;    HypT;    HOCl;    iron acquisition;    methionine oxidation;    630;   

Others  :  http://s-space.snu.ac.kr/bitstream/10371/141755/1/000000149653.pdf

美国|英语

来源: Seoul National University Open Repository

【 摘 要 】

Salmonella enterica serovar Typhimurium is one of the most common causes of food-borne illnesses. Despite many studies, no effective vaccine has been developed, and antibiotic therapy is also difficult that the alternative treatment is in great need. Hypochlorous acid (HOCl) is produced by immune system to kill invaded bacteria. HypT, a HOCl-specific transcription factor, is known to regulate several genes associated with HOCl-derived damage in Escherichia coli, but the detailed mechanism of HypT-mediated defense is not yet studied. This study investigated the mechanism of HypT-mediated defense in Salmonella enterica serovar Typhimurium SL1344. Based on the previous studies in E. coli, candidate genes were selected and transcription levels were compared. Expression of the genes related with iron acquisition was higher in the absence of hypT, indicating HypT represses the genes related with iron acquisition. HypT also repressed the genes related with iron acquisition in the absence of HOCl, and the repressive function was enhanced in the presence of HOCl. The difference in the expression of the genes related with iron acquisition was consistent to the phenotypes, and a higher level of intracellular iron content was detected in the absence of hypT. In addition, HypT was found to bind directly to the upstream of the promoter region of the iron acquisition genes to regulate the transcription level. The expression of the hypT was not influenced by HOCl, suggesting that HOCl may modulate HypT protein activity directly. Survival rate was decreased in the absence of hypT under NaOCl treatment condition, confirming the defense function of hypT against HOCl. Based on the previous research that Met123, Met206 and Met230 play important role in sensing HOCl and mechanism of activation of HypT proposed by the co-worker, I confirmed that the specific oxidation of methionine residue 206 is important for activation of HypT. These results suggest that HypT mitigates the overall oxidative stress by reducing the ROS produced spontaneously in the cell to cope with external HOCl stress.