• The Alkylquinolone Repertoire of Pseudomonas aeruginosa is Linked to Structural Flexibility of the FabH-like 2-Heptyl-3-hydroxy-4(1H)-quinolone (PQS) Biosynthesis Enzyme PqsBC.

      Witzgall, Florian; Depke, Tobias; Hoffmann, Michael; Empting, Martin; Brönstrup, Mark; Müller, Rolf; Blankenfeldt, Wulf; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Wiley-VCH, 2018-07-16)
      Pseudomonas aeruginosa is a bacterial pathogen that causes life-threatening infections in immunocompromised patients. It produces a large armory of saturated and mono-unsaturated 2-alkyl-4(1H)-quinolones (AQs) and AQ N-oxides (AQNOs) that serve as signaling molecules to control the production of virulence factors and that are involved in membrane vesicle formation and iron chelation; furthermore, they also have, for example, antibiotic properties. It has been shown that the β-ketoacyl-acyl-carrier protein synthase III (FabH)-like heterodimeric enzyme PqsBC catalyzes the last step in the biosynthesis of the most abundant AQ congener, 2-heptyl-4(1H)-quinolone (HHQ), by condensing octanoyl-coenzyme A (CoA) with 2-aminobenzoylacetate (2-ABA), but the basis for the large number of other AQs/AQNOs produced by P. aeruginosa is not known. Here, we demonstrate that PqsBC uses different medium-chain acyl-CoAs to produce various saturated AQs/AQNOs and that it also biosynthesizes mono-unsaturated congeners. Further, we determined the structures of PqsBC in four different crystal forms at 1.5 to 2.7 Å resolution. Together with a previous report, the data reveal that PqsBC adopts open, intermediate, and closed conformations that alter the shape of the acyl-binding cavity and explain the promiscuity of PqsBC. The different conformations also allow us to propose a model for structural transitions that accompany the catalytic cycle of PqsBC that might have broader implications for other FabH-enzymes, for which such structural transitions have been postulated but have never been observed.
    • Flexible Fragment Growing Boosts Potency of Quorum Sensing Inhibitors against Pseudomonas aeruginosa Virulence.

      Zender, Michael; Witzgall, Florian; Kiefer, Alexander Felix; Kirsch, Benjamin; Maurer, Christine K; Kany, Andreas M; Xu, Ningna; Schmelz, Stefan; Börger, Carsten; Blankenfeldt, Wulf; et al. (Wiley-VCH, 2019-11-11)
      Hit-to-lead optimization is a critical phase in drug discovery. Herein, we report on the fragment-based discovery and optimization of 2-amino pyridine derivatives as a novel lead-like structure for the treatment of the dangerous opportunistic pathogen Pseudomonas aeruginosa . We pursue an innovative treatment strategy by interfering with the Pseudomonas Quinolone Signal (PQS) Quorum Sensing (QS) system leading to an abolishment of bacterial pathogenicity. Our compounds act on the PQS receptor (PqsR), a key transcription factor controlling the expression of various pathogenicity determinants. In this target-driven approach, we made use of biophysical screening via surface plasmon resonance (SPR) followed by isothermal titration calorimetry (ITC)-enabled enthalpic efficiency (EE) evaluation. Hit optimization then involved growth vector identification and exploitation. Astonishingly, the latter was successfully achieved by introducing flexible linkers rather than rigid motifs leading to a boost in activity on the target receptor and anti-virulence potency.