Download citation
Download citation
link to html
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 2.30 Å 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 2.73 Å 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.

Supporting information

pdf

Portable Document Format (PDF) file https://doi.org/10.1107/S0907444913013802/mn5031sup1.pdf
Supplementary material

PDB references: TetX, complex with MTC, 4a99; complex with TTC, 4a6n; complex with Xe, 4guv


Follow Acta Cryst. D
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds