Cross-regulation of competence pheromone production and export in the early control of transformation in Streptococcus pneumoniae
Cross-regulation of competence pheromone production and export in the early control of transformation in Streptococcus pneumoniae
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DOI：
10.1046/j.1365-2958.2000.02187.x
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发表时间：
2000-11-01
影响因子：
3.6
通讯作者：
Claverys, JP
中科院分区：
文献类型：
--
作者：
Martin, B;Prudhomme, M;Claverys, JP
两个操纵子 comAB 和 comCDE 在协调肺炎链球菌培养物中的自发能力发展中发挥着关键作用，ComAB 是 comC 编码的能力刺激肽 (CSP) 输出所必需的，在 CSP 结合后，组氨酸激酶 ComD 激活 ComE，其同源反应调节器，是自诱导 comCDE 和诱导晚期能力基因所必需的，为了更好地了解能力发展的早期控制，使用comC-lacZ转录融合分离上调comCDE的突变体(ComCDE(UP))。通过comCDE区域的聚合酶链反应诱变和染色体的体外转座子诱变产生突变体。两种类型的ComCDEUP突变体都表现出相似的表型，与野生型的不同之处在于表现出胰蛋白酶抗性转化、酸性生长条件下的能力以及微需氧条件下comCDE的表达；突变体中 CSP 产量的增加可以解释各种表型，ComCDEUP 转座子突变包括 ciaR 基因中的四个独立插入，该基因编码先前发现影响能力的双组分系统的反应调节器，以及 comAB 操纵子上游的两个，后两个导致 comAB 过度表达，表明 CSP 输出受到速率限制。在 comDE 点突变中，ComD (T2331) 中的单个氨基酸变化赋予组成型、独立于 CSP 的能力，并导致 comAB 过度表达，为 ComE 调节 comAB 的假设提供支持； ComE 突变体 (R120S) 表现出能力关闭动力学的改变。总的来说，这些数据表明信息素自诱导、comAB 和 comCDE 操纵子的交叉调节以及可能的能力关闭有助于肺炎链球菌能力发展的早期控制。他们主张由 CiaR 直接或间接介导的能力代谢控制，并且他们表明 comAB 和 comCDE 都是潜在的调节目标。
Two operons, comAB and comCDE, play a key role in the co-ordination of spontaneous competence development in cultures of Streptococcus pneumoniae, ComAB is required for export of the comC-encoded competence-stimulating peptide (CSP), Upon CSP binding, the histidine kinase ComD activates ComE, its cognate response regulator, required for autoinduction of comCDE and for induction of the late competence genes, To understand better the early control of competence development, mutants upregulating comCDE (ComCDE(UP)) were isolated using a comC-lacZ transcriptional fusion, Mutants were generated by polymerase chain reaction mutagenesis of the comCDE region and by in vitro transposon mutagenesis of the chromosome. Both types of ComCDEUP mutants exhibited similar phenotypes, They differed from wild type in displaying trypsin-resistant transformation, competence under acid growth conditions and expression of comCDE under microaerobiosis; increased production of CSP in the mutants could account for the various phenotypes, The ComCDEUP transposon mutations included four independent insertions in the ciaR gene, which encodes the response regulator of a two-component system previously found to affect competence, and two immediately upstream of the comAB operon, The latter two resulted in comAB overexpression, indicating that CSP export is rate limiting, Among comDE point mutations, a single amino acid change in ComD (T2331) conferred constitutive, CSP-independent competence and resulted in comAB overexpression, providing support for the hypothesis that ComE regulates comAB; a ComE mutant (R120S) exhibited altered kinetics of competence shut-off, Collectively, these data indicate that pheromone autoinduction, cross-regulation of the comAB and comCDE operons and, possibly, competence shut-off contribute to the early control of competence development in S, pneumoniae, They argue for a metabolic control of competence, mediated directly or indirectly by CiaR, and they suggest that both comAB and comCDE are potential targets for regulation.