Figure 1.

Overview of MexR structure and DNA-binding properties and MexR dimer. (A) Schematic representation of MexAB-OprM multidrug efflux operon; arrows indicate the direction of transcription. Location of MexR regulatory DNA binding sites PI and PII in orange, PII sequence detailed with palindromes in gray, and direction in black arrows. (B) Crystal structure of a representative MexR homodimer in the absence of DNA in ribbon representation (1LNW:CD). Each secondary structure element is individually labeled and colored on the left monomer. The winged-HTH motif is colored in blue in the monomer on the right and comprises $\alpha$ 2 $\beta$ 1 $\alpha$ 3 $\alpha$ 4 $\beta$ 2 (recognition helix) W1 (wing)- $\beta$ 3. The distance between the two recognition helices ($\alpha$ 4/$\alpha$ 4′) is commonly reflected by the distance between Arg73-C${}_{\alpha }$ in the two monomers (indicated by yellow arrow). To see this figure in color, go online.