This domain is found at the C-terminal end of transcriptional regulators of the TetR family, including Swiss:O53623 from Mycobacterium tuberculosis and Swiss:Q1D4I5 from Myxococcus xanthus. This is the all-helical ligand-binding domain, which interacts with the respective effector molecule and transmits the signal to the DNA binding domain (Pfam:PF00440).

1: Reversion of antibiotic resistance in Mycobacterium tuberculosis by spiroisoxazoline SMARt-420. Blondiaux N, Moune M, Desroses M, Frita R, Flipo M, Mathys V, Soetaert K, Kiass M, Delorme V, Djaout K, Trebosc V, Kemmer C, Wintjens R, Wohlkonig A, Antoine R, Huot L, Hot D, Coscolla M, Feldmann J, Gagneux S, Locht C, Brodin P, Gitzinger M, Deprez B, Willand N, Baulard AR; Science. 2017;355:1206-1211. PMID:28302858

2: The AibR-isovaleryl coenzyme A regulator and its DNA binding site - a model for the regulation of alternative de novo isovaleryl coenzyme A biosynthesis in Myxococcus xanthus. Bock T, Volz C, Hering V, Scrima A, Muller R, Blankenfeldt W; Nucleic Acids Res. 2017;45:2166-2178. PMID:27940564

3: Cytokinin Signaling in Mycobacterium tuberculosis. Samanovic MI, Hsu HC, Jones MB, Jones V, McNeil MR, Becker SH, Jordan AT, Strnad M, Xu C, Jackson M, Li H, Darwin KH; mBio. 2018; [Epub ahead of print] PMID:29921668