Helix-Turn-Helix DNA binding domain of the CadR- and PbrR-like transcription regulators
Helix-turn-helix (HTH) CadR- and PbrR-like transcription regulators. CadR and PbrR regulate expression of the cadmium and lead resistance operons, respectively. These proteins are comprised of distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their conserved N-terminal domains contain predicted winged HTH motifs that mediate DNA binding, while the C-terminal domains have three conserved cysteines which comprise a putative metal binding site. Some members in this group have a histidine-rich C-terminal extension. These proteins share the N-terminal DNA binding domain with other transcription regulators of the MerR superfamily that promote transcription by reconfiguring the spacer between the -35 and -10 promoter elements.