Regulation of the glucosyltransferase (gtfBC) operon by CovR in Streptococcus mutans
Regulation of the glucosyltransferase (gtfBC) operon by CovR in Streptococcus mutans
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DOI：
10.1128/jb.188.3.988-998.2006
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发表时间：
2006-02-01
影响因子：
3.2
通讯作者：
Biswas, I
中科院分区：
文献类型：
--
作者：
Biswas, S;Biswas, I
变形链球菌是人类龋齿的重要病原体。由细胞相关葡糖基转移酶（由gtfBC编码）从蔗糖合成的胞外多糖已被认为是促进细胞聚集和粘附于牙齿，导致牙菌斑形成的重要毒力因子之一。在这项研究中，我们的特点是CovR，一个全球性的反应调节，对葡萄糖基转移酶的表达的影响。covR在菌株UA 159中的失活导致GtfB和GtfC蛋白的显着增加，通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析。通过使用PgtfB-gusA和PgtfC-gusA融合体的单个染色体拷贝的转录报告系统，我们证实了CovR对这些启动子的转录调控。通过纯化的CovR蛋白的体外电泳迁移率变动分析，我们表明CovR直接调节这些启动子。DNA酶I足迹分析表明，CovR结合到这些启动子上靠近转录起始位点的大区域。总之，我们的结果表明，CovR负调控gtfB和gtfC基因的表达直接结合到启动子区。
Streptococcus mutans is an important etiological agent of dental caries in humans. The extracellular polysaccharides synthesized by cell-associated glucosyltransferases (encoded by gtfBC) from sucrose have been recognized as one of the important virulence factors that promote cell aggregation and adherence to teeth, leading to dental plaque formation. In this study, we have characterized the effect of CovR, a global response regulator, on glucosyltransferase expression. Inactivation of covR in strain UA159 resulted in a marked increase in the GtfB and GtfC proteins, as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. With the use of a transcriptional reporter system of a single chromosomal copy of the PgtfB-gusA and PgtfC-gusA fusions, we confirmed the transcriptional regulation of these promoters by CovR. By in vitro electrophoretic mobility shift assays with purified CovR protein, we showed that CovR regulates these promoters directly. DNase I footprinting analyses suggest that CovR binds to large regions on these promoters near the transcription start sites. Taken together, our results indicate that CovR negatively regulates the expression of the gtfB and gtfC genes by directly binding to the promoter region.