Ligand-binding domain of DNA transcription repressor RegR and other putative regulators such as KdgR and EndR
Ligand-binding domain of DNA transcription repressor RegR and other putative regulators such as KdgR and EndR, all of which are members of the LacI-GalR family of bacterial transcription regulators. RegR regulates bacterial competence and the expression of virulence factors, including hyaluronidase. The LacI-GalR family repressors are composed of two functional domains: an N-terminal HTH (helix-turn-helix) domain, which is responsible for the DNA-binding specificity, and a C-terminal ligand-binding domain, which is homologous to the sugar-binding domain of ABC-type transport systems that contain the type I periplasmic binding protein-like fold. As also observed in the periplasmic binding proteins, the C-terminal domain of the bacterial transcription repressor undergoes a conformational change upon ligand binding which in turn changes the DNA binding affinity of the repressor.