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首页> 外文期刊>Infection and immunity >Analysis of a Heme-Dependent Signal Transduction System in Corynebacterium diphtheriae: Deletion of the chrAS Genes Results in Heme Sensitivity and Diminished Heme-Dependent Activation of the hmuO Promoter
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Analysis of a Heme-Dependent Signal Transduction System in Corynebacterium diphtheriae: Deletion of the chrAS Genes Results in Heme Sensitivity and Diminished Heme-Dependent Activation of the hmuO Promoter

机译：白喉棒状杆菌中血红素依赖性信号转导系统的分析：chrAS基因的删除导致血红素敏感性和hmuO启动子的血红素依赖性激活减少。

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The Corynebacterium diphtheriae hmuO gene encodes a heme oxygenase that is involved in the utilization of heme as an iron source. Transcription of hmuO is activated by heme or hemoglobin and repressed by iron and DtxR. Previous studies with Escherichia coli showed that heme-dependent transcriptional activation of an hmuO promoter-lacZ fusion was dependent on the cloned C. diphtheriae chrA and chrS genes (chrAS), which encode the response regulator and sensor kinase, respectively, of a two-component signal transduction system. In this study, nonpolar deletions in the chrAS genes were constructed on the chromosome of C. diphtheriae. Mutations in chrAS resulted in marked reduction in heme-dependent transcription of hmuO, which indicates that the ChrA/S system is a key regulator at the hmuO promoter. However, low but significant levels of heme-specific transcriptional activity were observed at the hmuO promoter in the chrAS mutants, suggesting that an additional heme-dependent activator is involved in hmuO expression. The chrAS mutants were also sensitive to heme, which was observed only in stationary-phase cultures and correlated with reduced cell viability. The heme sensitivity of the mutants was not due to reduced expression of hmuO, and these results suggest that additional factors controlled by the ChrA/S system may be involved in protection against heme toxicity. Transcriptional analysis of the chrAS operon revealed that it was not autoregulated or affected by iron or heme levels.
机译：白喉棒状杆菌hmuO 基因编码一个血红素加氧酶，该酶与利用血红素作为铁源有关。 hmuO 的转录被血红素或血红蛋白激活，并被铁和DtxR抑制。以前对大肠杆菌的研究表明， hmuO 启动子- lacZ 融合物的血红素依赖性转录激活取决于克隆的 C。白喉菌chrA 和 chrS 基因（ chrAS ）分别编码两组分信号转导系统的响应调节因子和传感器激酶。在这项研究中，在 C染色体上构建了 chrAS 基因的非极性缺失。白喉。 chrAS 中的突变导致 hmuO 的血红素依赖性转录显着降低，这表明ChrA / S系统是 hmuO 启动子。但是，在 chrAS 突变体的 hmuO 启动子上观察到了低水平但显着水平的血红素特异性转录活性，这表明中还涉及了一种其他的血红素依赖性激活剂。 > hmuO 表达式。 chrAS 突变体也对血红素敏感，这仅在固定相培养中观察到，并且与细胞活力降低有关。突变体的血红素敏感性不是由于 hmuO 的表达降低，这些结果表明，由ChrA / S系统控制的其他因素可能参与了血红素毒性的保护作用。对 r 操纵子的转录分析表明，它不受铁或血红素水平的自动调节或影响。

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