The transcription regulator TcaR is a member of the MarR family, and is involved in teicoplanin and methicillin resistance in Staphylococci [5] . The MarR family proteins function as regulators of protein expression and these regulated proteins confer resistance to multiple antibiotics, household disinfectants, organic solvent virulence factors, and oxidative stress agents [6, 7, 8, 9, 10, 11] . The crystal structures of a number of MarR family proteins have been reported, including MarR from Escherichia coli [12] , OhrR from Bacillis subtilis [13] , MexR from Pseudomonas aeruginosa [14] , MarR from Xanthomonas campestris [15] , SlyA from Salmonella typhimurium [16] , AdcR from Streptococcus pneumonia [10] and TcaR, which is studied in this work, from S. epidermidis [17] . These structures revealed that MarR family proteins are all homodimers. The overall structure of each monomer could be divided into two functional domains, one is the dimerization domain and the other is the winged helix-turn-helix (wHTH) DNA binding domain. The N and the C-terminal a-helices (a1, 5, 6) of one monomer interdigitate with those of the other monomer to produce dimerization interaction. In addition, the wHTH DNA binding domain is composed of a2-a3-a4-bA-W1-bB which adopts the winged-helix-fold, and the amino acid sequences of this domain are highly conserved.