Anhydrotetracycline (hydrochloride) (ATC) is a powerful effector for the tetracycline repressor (TetR) and reverse tetracycline repressor (revTetR) systems [1].

Tetracycline repressor (TetR) is an effector-regulated DNA-binding protein that binds tightly to its palindromic tetO operator DNA in the absence of effector, thereby blocking the transcription of any downstream genes. Binding of tetracycline (TC) or anhydrote-tracycline (ATC) to TetR causes the repressor to dissociate from the DNA and gene transcription can occur. Contrary to TetR, reverse tetracycline repressor (revTetR) mutant binds tetO only in the presence of ATC [2][3].

Anhydrotetracycline (hydrochloride) is a powerful effector for TetR and revTetR systems. Anhydrotetracycline (ATC) bound TetR with a 500-fold higher affinity and represented the most efficient inducer [2]. ATC bound the Tet repressor 35-fold more potent than Tet [4]. However, ATC acted as a corepressor in revTetR variant. In β-galactosidase (β-gal) assays, TetR inhibitedβ-gal expression to nearly 1%, while ~100% expression was accomplished in the presence of 0.4 μM ATC. RevTetR produced almost 100%β-gal activity in the absence of ATC, while the presence of 0.4 μM ATC resulted in a 5-fold decrease ofβ-gal activity [2].

References:
[1].  Gossen M, Bujard H. Anhydrotetracycline, a novel effector for tetracycline controlled gene expression systems in eukaryotic cells. Nucleic Acids Res. 1993 Sep 11;21(18):4411-2.
[2].  Kamionka A, Bogdanska-Urbaniak J, Scholz O, et al. Two mutations in the tetracycline repressor change the inducer anhydrotetracycline to a corepressor. Nucleic Acids Res. 2004 Feb 4;32(2):842-7.
[3].  Resch M, Striegl H, Henssler EM, et al. A protein functional leap: how a single mutation reverses the function of the transcription regulator TetR. Nucleic Acids Res. 2008 Aug;36(13):4390-401.
[4].  Degenkolb J, Takahashi M, Ellestad GA, et al. Structural requirements of tetracycline-Tet repressor interaction: determination of equilibrium binding constants for tetracycline analogs with the Tet repressor. Antimicrob Agents Chemother. 1991 Aug;35(8):1591-5.