title: Structural basis for a new tetracycline resistance mechanism relying on the TetX monooxygenase.
abstract: The flavin-dependent monooxygenase TetX confers resistance to all clinically relevant tetracyclines, including the recently approved, broad-spectrum antibiotic tigecycline (Tygacil®) which is a critical last-ditch defense against multidrug-resistant pathogens. TetX represents the first resistance mechanism against tigecycline, which circumvents both the tet-gene encoded resistances, relying on active efflux of tetracyclines, and ribosomal protection proteins. The alternative enzyme-based mechanism of TetX depends on regioselective hydroxylation of tetracycline antibiotics to 11a-hydroxy-tetracyclines. Here, we report the X-ray crystallographic structure determinations at 2.1Å resolution of native TetX from Bacteroides thetaiotaomicron and its complexes with tetracyclines. Our crystal structures explain the extremely versatile substrate diversity of the enzyme and provide a first step towards the rational design of novel tetracycline derivatives to counter TetX-based resistance prior to emerging clinical observations.
authors.affiliation: Institut für Biochemie, Universität Greifswald, Greifswald, Germany.
authors.forename: Gesa
authors.initials: G
authors.lastname: Volkers
authors.forename: Gottfried J
authors.initials: GJ
authors.lastname: Palm
authors.forename: Manfred S
authors.initials: MS
authors.lastname: Weiss
authors.forename: Gerard D
authors.initials: GD
authors.lastname: Wright
authors.forename: Winfried
authors.initials: W
authors.lastname: Hinrichs
mesh_terms: D001439:Bacteroides / Q000187:drug effects* / Q000201:enzymology*; D001665:Binding Sites; D018360:Crystallography, X-Ray; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013752:Tetracycline / Q000378:metabolism / Q000494:pharmacology*; D013753:Tetracycline Resistance
chemical_list: D005182:Flavin-Adenine Dinucleotide; D006899:Mixed Function Oxygenases; D013752:Tetracycline; D010100:Oxygen