JBIC Journal of Biological Inorganic Chemistry

, 13:1097

Specific binding of divalent metal ions to tetracycline and to the Tet repressor/tetracycline complex


  • Gottfried J. Palm
    • Institut für BiochemieUniversität Greifswald
  • Thomas Lederer
    • Institut für MikrobiologieUniversität Erlangen-Nürnberg
  • Peter Orth
    • Institut für Chemie und Biochemie/KristallographieFreie Universität Berlin
    • Schering-Plough
  • Wolfram Saenger
    • Institut für Chemie und Biochemie/KristallographieFreie Universität Berlin
  • Masayuki Takahashi
    • UMR 6204 Centre National de la Recherche Scientifique and Universite de Nantes
  • Wolfgang Hillen
    • Institut für MikrobiologieUniversität Erlangen-Nürnberg
    • Institut für BiochemieUniversität Greifswald
Original Paper

DOI: 10.1007/s00775-008-0395-2

Cite this article as:
Palm, G.J., Lederer, T., Orth, P. et al. J Biol Inorg Chem (2008) 13: 1097. doi:10.1007/s00775-008-0395-2


Tetracyclines coordinate metal(II) ions under physiological conditions forming chelate complexes with their ketoenolate moiety at rings B and C. These metal(II) complexes are the biologically relevant molecules conferring the antibiotic character of the drug by inhibiting ribosomal protein biosynthesis in prokaryotes. The Tet repressor, TetR, is the molecular switch for tetracycline resistance determinants in gram-negative bacteria. TetR controls transcription of a gene encoding the integral membrane protein TetA, which mediates active efflux of a tetracycline–metal(II) cation, [MeTc]+, by equimolar antiport with a proton. We evaluated distinct characteristics of the metal binding by crystal structure determination of TetR/[MeTc]+ complexes and of association equilibrium constants of [MeTc]+ and TetR/[MeTc]+ complexes. Various divalent metal ions bind to the same octahedral coordination site, defined by a histidine side chain of TetR, the tetracycline, and three water molecules. Whereas association constants for [MeTc]+ vary within 3 orders of magnitude, association of the [MeTc]+ cation to TetR is very similar for all measured divalent metals. Taking intracellular cation concentrations into account, it is evident that no other metal ion can compete with Mg2+ for TetR/[MeTc]+ complex formation.


Binding affinityX-ray crystallographyStructure–function relationshipMetalloregulationTetracycline

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© SBIC 2008