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首页> 外文期刊>Applied Microbiology >Role of GlnR in Acid-Mediated Repression of Genes Encoding Proteins Involved in Glutamine and Glutamate Metabolism in Streptococcus mutans
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Role of GlnR in Acid-Mediated Repression of Genes Encoding Proteins Involved in Glutamine and Glutamate Metabolism in Streptococcus mutans

机译：GlnR在酸介导的抑制变形链球菌谷氨酰胺和谷氨酸代谢相关蛋白的基因的调控中的作用。

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The acid tolerance response (ATR) is one of the major virulence traits of Streptococcus mutans . In this study, the role of GlnR in acid-mediated gene repression that affects the adaptive ATR in S. mutans was investigated. Using a whole-genome microarray and in silico analyses, we demonstrated that GlnR and the GlnR box (ATGTNAN_(7)TNACAT) were involved in the transcriptional repression of clusters of genes encoding proteins involved in glutamine and glutamate metabolism under acidic challenge. Reverse transcription-PCR (RT-PCR) analysis revealed that the coordinated regulation of the GlnR regulon occurred 5 min after acid treatment and that prolonged acid exposure (30 min) resulted in further reduction in expression. A lower level but consistent reduction in response to acidic pH was also observed in chemostat-grown cells, confirming the negative regulation of GlnR. The repression by GlnR through the GlnR box in response to acidic pH was further confirmed in the citBZC operon, containing genes encoding the first three enzymes in the glutamine/glutamate biosynthesis pathway. The survival rate of the GlnR-deficient mutant at pH 2.8 was more than 10-fold lower than that in the wild-type strain 45 min after acid treatment, suggesting that the GlnR regulon participates in S. mutans ATR. It is hypothesized that downregulation of the synthesis of the amino acid precursors in response to acid challenge would promote citrate metabolism to pyruvate, with the consumption of H~(+) and potential ATP synthesis. Such regulation will ensure an optimal acid adaption in S. mutans .
机译：耐酸反应（ATR）是变形链球菌的主要毒力特征之一。在这项研究中，研究了GlnR在酸介导的基因抑制中影响变形链球菌适应性ATR的作用。使用全基因组微阵列和计算机模拟分析，我们证明了GlnR和GlnR框（ATGTNAN_（7）TNACAT）参与编码在酸性挑战下涉及谷氨酰胺和谷氨酸代谢的蛋白质的基因簇的转录抑制。逆转录PCR（RT-PCR）分析显示，在酸处理后5分钟发生了对GlnR调节子的协调调控，而延长的酸暴露时间（30分钟）导致表达进一步降低。在恒化器生长的细胞中也观察到较低水平但对酸性pH的响应持续降低，这证实了GlnR的负调控。在citBZC操纵子中进一步证实了通过GlnR通过GlnR盒对酸性pH的抑制，所述操纵子包含编码谷氨酰胺/谷氨酸生物合成途径中前三个酶的基因。酸处理后45分钟，pH 2.8时GlnR缺陷型突变体的存活率比野生型菌株低10倍以上，这表明GlnR调节子参与了变形链球菌ATR。假设响应于酸激发而下调氨基酸前体的合成将促进柠檬酸盐代谢为丙酮酸，同时消耗H〜（+）和潜在的ATP合成。这样的调节将确保变形链球菌的最佳酸适应性。

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