Characterization of MbrC involved in bacitracin resistance in Streptococcus mutans

Norio Kitagawa, Susumu Shiota, Yukie Shibata, Toru Takeshita, Yoshihisa Yamashita

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12 Citations (Scopus)


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 (D54N-MbrC) that substituted asparagine for aspartate at position 54, the predicted phosphorylation site. MbrC, but not the mutant D54N-MbrC, showed affinity for a DNA probe that contained the hypothetical mbrA promoter sequence. Furthermore, we introduced a point mutation (D54N-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.

Original languageEnglish
Pages (from-to)61-67
Number of pages7
JournalFEMS microbiology letters
Issue number1
Publication statusPublished - May 2011

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Molecular Biology
  • Genetics


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