Transcriptional analysis of the bglP gene from Streptococcus mutans

BACKGROUND: An open reading frame encoding a putative antiterminator protein, LicT, was identified in the genomic sequence of Streptococcus mutans. A potential ribonucleic antitermination (RAT) site to which the LicT protein would potentially bind has been identified immediately adjacent to this open reading frame. The licT gene and RAT site are both located 5' to a beta-glucoside PTS regulon previously described in S. mutans that is responsible for esculin utilization in the presence of glucose. It was hypothesized that antitermination is the regulatory mechanism that is responsible for the control of the bglP gene expression, which encodes an esculin-specific PTS enzyme II. RESULTS: To localize the promoter activity associated with the bglP locus, a series of transcriptional lacZ gene fusions was formed on a reporter shuttle vector using various DNA fragments from the bglP promoter region. Subsequent beta-galactosidase assays in S. mutans localized the bglP promoter region and identified putative -35 and -10 promoter elements. Primer extension analysis identified the bglP transcriptional start site. In addition, a terminated bglP transcript formed by transcriptional termination was identified via transcript mapping experiments. CONCLUSION: The physical location of these genetic elements, the RAT site and the promoter regions, and the identification of a short terminated mRNA support the hypothesis that antitermination regulates the bglP transcript.