Regulation of the glucosyltransferase (gtfBC) operon by CovR in Streptococcus mutans.
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.
Biswas
Saswati
S
Division of Basic Biomedical Sciences, University of South Dakota School of Medicine, Lee Medical Building, 414 East Clark Street, Vermillion, SD 57069. ibiswas@usd.edu.
Biswas
Indranil
I
D001426:Bacterial Proteins / Q000502:physiology*; D001665:Binding Sites / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism*; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D013295:Streptococcus mutans / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D013395:Sucrose / Q000378:metabolism
D001426:Bacterial Proteins; C432143:CsrR protein, Streptococcus pyogenes; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D013395:Sucrose; D005964:Glucosyltransferases