Oxidative stress response of Deinococcus geothermalis via a cystine importer

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• 作者：Minwook Kim ; Sunwook Jeong ; Sangyong Lim ; Jeonggu Sim…
• 关键词：Deinococcus geothermalis ; oxidative ; stress response ; H2O2 scavenger ; cystine importer ; anti ; oxidation
• 刊名：Journal of Microbiology
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：55
• 期：2
• 页码：137-146
• 全文大小：
• 刊物主题：Microbiology;
• 出版者：The Microbiological Society of Korea
• ISSN：1976-3794
• 卷排序：55

文摘

A cystine-dependent anti-oxidative stress response is characterized in Deinococcus geothermalis for the first time. Nevertheless, the same transcriptional directed Δdgeo_1985F mutant strain was revealed to have an identical phenotype to the wild-type strain, while the reverse transcriptional directed Δdgeo_1985R mutant strain was more resistant to oxidative stress at a certain concentration of H<sub>2sub>O<sub>2sub> than the wild-type strain. The wild-type and mutant strains expressed equal levels of superoxide dismutase and catalase under H<sub>2sub>O<sub>2sub>-induced stress. Although the expression levels of the general DNA-damage response-related genes recA, pprA, ddrA, and ddrB were up-regulated by more than five-fold in the wild-type strain relative to the Δdgeo_1985R mutant strain, the mutant strain had a higher survival rate than the wild-type under H<sub>2sub>O<sub>2sub> stress. The Δdgeo_1985R mutant strain highly expressed a cystine-transporter gene (dgeo_1986), at levels 150-fold higher than the wild-type strain, leading to the conclusion that this cystine transporter might be involved in the defensive response to H<sub>2sub>O<sub>2sub> stress. In this study, the cystine transporter was identified and characterized through membrane protein expression analysis, a cystine-binding assay, and assays of intracellular H<sub>2sub>O<sub>2sub>, cysteine, and thiol levels. The genedisrupted mutant strain of the cystine importer revealed high sensitivity to H<sub>2sub>O<sub>2sub> and less absorbed cystine, resulting in low concentrations of total thiol. Thus, the absorbed cystine via this cystine-specific importer may be converted into cysteine, which acts as a primitive defense substrate that non-enzymatically scavenges oxidative stress agents in D. geothermalis.