Putative dioxygen-binding sites and recognition of tigecycline and minocycline in the tetracycline-degrading monooxygenase TetX

Gesa Volkers, João M. Damas, Gottfried J. Palm, Santosh Panjikar, Cláudio M. Soares, Winfried Hinrichs

Research output: Contribution to journalArticleResearchpeer-review

28 Citations (Scopus)

Abstract

Expression of the aromatic hydroxylase TetX under aerobic conditions confers bacterial resistance against tetracycline antibiotics. Hydroxylation inactivates and degrades tetracyclines, preventing inhibition of the prokaryotic ribosome. X-ray crystal structure analyses of TetX in complex with the second-generation and third-generation tetracyclines minocycline and tigecycline at 2.18 and 2.30Å resolution, respectively, explain why both clinically potent antibiotics are suitable substrates. Both tetracyclines bind in a large tunnel-shaped active site in close contact to the cofactor FAD, pre-oriented for regioselective hydroxylation to 11a-hydroxytetracyclines. The characteristic bulky 9-tert-butylglycylamido substituent of tigecycline is solvent-exposed and does not interfere with TetX binding. In the TetX-minocycline complex a second binding site for a minocycline dimer is observed close to the active-site entrance. The pocket is formed by the crystal packing arrangement on the surface of two neighbouring TetX monomers. Crystal structure analysis at 2.73Å resolution of xenon-pressurized TetX identified two adjacent Xe-binding sites. These putative dioxygen-binding cavities are located in the substrate-binding domain next to the active site. Molecular-dynamics simulations were performed in order to characterize dioxygen-diffusion pathways to FADH2 at the active site.

Original languageEnglish
Pages (from-to)1758-1767
Number of pages10
JournalActa Crystallographica Section D: Biological Crystallography
Volume69
Issue number9
DOIs
Publication statusPublished - Sept 2013
Externally publishedYes

Keywords

  • antibiotic resistance
  • dioxygen diffusion
  • minocycline
  • molecular dynamics
  • monooxygenases
  • simulation
  • TetX
  • tigecycline
  • xenon

Cite this