title: The pH-dependent expression of the urease operon in Streptococcus salivarius is mediated by CodY.
abstract: Urease gene expression in Streptococcus salivarius 57.I, a strain of one of the major alkali producers in the mouth, is induced by acidic pH and excess amounts of carbohydrate. Expression is controlled primarily at the transcriptional level from a promoter, pureI. Recent sequencing analysis revealed a CodY box located 2 bases 5' to the -35 element of pureI. Using continuous chemostat culture, transcription from pureI was shown to be repressed by CodY, and at pH 7 the repression was more pronounced than that in cells grown at pH 5.5 under both 20 and 100 mM glucose. The direct binding of CodY to pureI was demonstrated by electrophoretic mobility shift assay and chromatin immunoprecipitation (ChIP)-quantitative real-time PCR (qPCR). The result of ChIP-qPCR also confirmed that the regulation of CodY is indeed modulated by pH and the binding of CodY at neutral pH is further enhanced by a limited supply of glucose (20 mM). In the absence of CodY, the C-terminal domain of the RNA polymerase (RNAP) α subunit interacted with the AT tracks within the CodY box, indicating that CodY and RNAP compete for the same binding region. Such regulation could ensure optimal urease expression when the enzyme is most required, i.e., at an acidic growth pH with an excess amount of carbon nutrients.
authors.affiliation: Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan.
authors.forename: Szu-Chuan
authors.initials: SC
authors.lastname: Huang
authors.affiliation: Department of Oral Biology, University of Florida, Gainesville, Florida, USA.
authors.forename: Robert A
authors.initials: RA
authors.lastname: Burne
authors.affiliation: Department of Microbiology and Immunology, College of Medicine, Chang Gung University, Taoyuan, Taiwan Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan, Taiwan Research Center for Pathogenic Bacteria, College of Medicine, Chang Gung University, Taoyuan, Taiwan mchen@mail.cgu.edu.tw.
authors.forename: Yi-Ywan M
authors.initials: YY
authors.lastname: Chen
mesh_terms: D050260:Carbohydrate Metabolism; D047369:Chromatin Immunoprecipitation; D004269:DNA, Bacterial / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D006863:Hydrogen-Ion Concentration; D009876:Operon; D011485:Protein Binding; D060888:Real-Time Polymerase Chain Reaction; D012097:Repressor Proteins / Q000378:metabolism*; D013291:Streptococcus / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics; D014510:Urease / Q000096:biosynthesis*
chemical_list: D004269:DNA, Bacterial; D012097:Repressor Proteins; D014510:Urease