title: Characterization of MbrC involved in bacitracin resistance in Streptococcus mutans.
abstract: Streptococcus mutans, a major etiological agent of dental caries, is resistant to bacitracin. Microarray analysis revealed that mbrA and mbrB, encoding a putative ATP-binding cassette transporter, are prominently induced in the presence of bacitracin. On the basis of the latest report that MbrC, a putative response regulator in a two-component signaling system, binds the promoter region of mbrA and thus regulates its transcription, we cut into the mechanism by generating a mutant MbrC (D(54) N-MbrC) that substituted asparagine for aspartate at position 54, the predicted phosphorylation site. MbrC, but not the mutant D(54) N-MbrC, showed affinity for a DNA probe that contained the hypothetical mbrA promoter sequence. Furthermore, we introduced a point mutation (D(54) N-MbrC) into UA159; this mutant strain exhibited neither mbrA induction nor resistance in the presence of bacitracin. These data suggest that the aspartate residue at position 54 of MbrC is a promising candidate for phosphorylation in a bacitracin-sensing system and indispensable for S. mutans bacitracin resistance.
authors.affiliation: Section of Preventive and Public Health Dentistry, Division of Oral Health, Growth and Development, Kyushu University Faculty of Dental Science, Fukuoka, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Kitagawa
authors.forename: Susumu
authors.initials: S
authors.lastname: Shiota
authors.forename: Yukie
authors.initials: Y
authors.lastname: Shibata
authors.forename: Toru
authors.initials: T
authors.lastname: Takeshita
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Yamashita
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001414:Bacitracin / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D024881:Drug Resistance, Bacterial; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016415:Sequence Alignment; D013295:Streptococcus mutans / Q000737:chemistry / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001414:Bacitracin