Helix-Turn-Helix DNA binding domain of putative Cfa-like transcription regulators
Putative helix-turn-helix (HTH) MerR-like transcription regulator; conserved, Cfa-like, unknown proteins (~172 a.a.). The N-terminal domain of these proteins appears to be related to the HTH domain of Cfa, a cyclopropane fatty acid synthase. These Cfa-like proteins have a unique C-terminal domain with conserved histidines (motif HXXFX7HXXF). Based on sequence similarity of the N-terminal domains, these proteins are predicted to function as transcription regulators that mediate responses to stress in eubacteria. They belong to the MerR superfamily of transcription regulators that promote transcription of various stress regulons by reconfiguring the operator sequence located between the -35 and -10 promoter elements. A typical MerR regulator is comprised of distinct domains that harbor the regulatory (effector-binding) site and the active (DNA-binding) site. Their N-terminal domains are homologous and contain a DNA-binding winged HTH motif, while the C-terminal domains are often dissimilar and bind specific coactivator molecules such as metal ions, drugs, and organic substrates.