This family of bacterial transcriptional repressors is characterised by the short approximately 50 amino acid stretch of residues constituting the helix-turn-helix DNA binding motif, around the YRFhY motif. The target proteins that are repressed are involved in the transcriptional control of multi-drug efflux pumps, pathways for the biosynthesis of antibiotics, response to osmotic stress and toxic chemicals, control of catabolic pathways, differentiation processes, and pathogenicity. The regulatory network in which TetR itself is involved is in being released in the presence of tetracycline, binding to the target operator, and repressing tetA transcription [1].

1: The TetR family of transcriptional repressors. Ramos JL, Martinez-Bueno M, Molina-Henares AJ, Teran W, Watanabe K, Zhang X, Gallegos MT, Brennan R, Tobes R; Microbiol Mol Biol Rev. 2005;69:326-356. PMID:15944459