RESUMO
Streptococcus mutans is implicated in human dental caries, and the carbohydrate metabolism of this organism plays an important role in the formation of this disease. Carbohydrate transport and metabolism are essential for the survival of S. mutans in the oral cavity. It is known that a unique phosphoenolpyruvate-sugar phosphotransferase system PTS(B) (io) of S. mutans UA159 is expressed in sucrose-grown biofilms (Mol Oral Microbiol 28: 2013; 114). In this study we analyzed the transcriptional regulation of the operon (O(B) (io) ) encoding the PTS(B) (io) and showed that it was repressed by NigR, a LacI-like transcriptional regulator. Using electro-mobility shift assay, we described two operators to which NigR bound with different affinities. We also identified the transcriptional start site and showed that one of the operators overlaps with the promoter and presumably represses initiation of transcription. Mutational analyses revealed the key nucleotides in the operators required for high-affinity binding of NigR. PTS(B) (io) is expressed in S. mutans biofilms so understanding its regulation may provide improved strategies for caries treatment and prevention.
Assuntos
Proteínas de Bactérias/metabolismo , Regulação Bacteriana da Expressão Gênica , Regiões Operadoras Genéticas , Sistema Fosfotransferase de Açúcar do Fosfoenolpiruvato/genética , Proteínas Repressoras/metabolismo , Streptococcus mutans/genética , Proteínas de Bactérias/genética , Biofilmes , Transporte Biológico/genética , Cárie Dentária/microbiologia , Genes Bacterianos , Humanos , Repressores Lac/genética , Mutagênese , Óperon , Regiões Promotoras Genéticas , Ligação Proteica , Proteínas Repressoras/genética , Streptococcus mutans/metabolismo , Sítio de Iniciação de Transcrição , Transcrição GênicaRESUMO
The DNA sequence C/AGAGCGC/AGA, related to binding sites for GAF and Zeste transcription factors, was selected from a pool of degenerate PCR fragments for binding to the cytoplasmic protein of Drosophila preblastoderm embryos. Identical DNA binding activity was also detected in embryonic nuclei. Based on several criteria, such as size, intracellular distribution, sensitivity to ATP and protein kinase inhibitor 6-DMAP, kinetics during development and lack of cross-reaction with rabbit anti-GAF serum, protein recognizing selected sequence was shown to differ from either Zeste or GAF.
