ABSTRACT
Increasing antibiotic resistance urgently requires novel therapeutic options to combat bacterial infections. The anti-virulence therapy selectively intervening with pathogenicity without affecting bacterial viability is such a strategy to overcome resistance. We consider the virulence regulator PqsR as an attractive target in the human pathogen Pseudomonas aeruginosa, and recently discovered the first PqsR antagonists, which, however, suffered from poor aqueous solubility. In this work, the antagonists were structurally modified to become more soluble, and their structure-activity as well as structure-property relationships were studied. A novel promising compound with improved solubility and enhanced anti-virulence activity was discovered (IC50: 3.8 µM, pyocyanin). Our findings emphasize the crucial role of substituents at the 3-position and the carbonyl group at the 4-position for ligand-receptor interactions, and illuminate the way for further optimization of PqsR antagonists as anti-virulence agents.
Subject(s)
Anti-Bacterial Agents/pharmacology , Pseudomonas aeruginosa/drug effects , Quinolones/antagonists & inhibitors , Anti-Bacterial Agents/chemical synthesis , Anti-Bacterial Agents/chemistry , Dose-Response Relationship, Drug , Microbial Sensitivity Tests , Molecular Structure , Pseudomonas aeruginosa/pathogenicity , Quorum Sensing/drug effects , Solubility , Structure-Activity Relationship , Virulence/drug effects , Water/chemistryABSTRACT
Pseudomonas aeruginosa employs a characteristic pqs quorum sensing (QS) system that functions via the signal molecules PQS and its precursor HHQ. They control the production of a number of virulence factors and biofilm formation. Recently, we have shown that sulfonamide substituted 2-benzamidobenzoic acids, which are known FabH inhibitors, are also able to inhibit PqsD, the enzyme catalyzing the last and key step in the biosynthesis of HHQ. Here, we describe the further optimization and characterization of this class of compounds as PqsD inhibitors. Structural modifications showed that both the carboxylic acid ortho to the amide and 3'-sulfonamide are essential for binding. Introduction of substituents in the anthranilic part of the molecule resulted in compounds with IC50 values in the low micromolar range. Binding mode investigations by SPR with wild-type and mutated PqsD revealed that this compound class does not bind into the active center of PqsD but in the ACoA channel, preventing the substrate from accessing the active site. This binding mode was further confirmed by docking studies and STD NMR.
Subject(s)
Bacterial Proteins/antagonists & inhibitors , Benzamides/chemical synthesis , Benzoates/chemical synthesis , Enzyme Inhibitors/chemical synthesis , Pseudomonas aeruginosa/drug effects , Quorum Sensing , Sulfonamides/chemical synthesis , Transcription Factors/antagonists & inhibitors , 4-Quinolones/metabolism , Benzamides/chemistry , Benzamides/pharmacology , Benzoates/chemistry , Benzoates/pharmacology , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Magnetic Resonance Spectroscopy , Molecular Docking Simulation , Protein Binding , Pseudomonas Infections/microbiology , Pseudomonas aeruginosa/enzymology , Quinolones/metabolism , Structure-Activity Relationship , Sulfonamides/chemistry , Sulfonamides/pharmacology , Surface Plasmon ResonanceABSTRACT
Ovothiols are histidine-derived thiols that were first isolated from marine invertebrates. We have identified a 5-histidylcysteine sulfoxide synthase (OvoA) as the first ovothiol biosynthetic enzyme and characterized OvoAs from Erwinia tasmaniensis and Trypanosoma cruzi . Homologous enzymes are encoded in more than 80 genomes ranging from proteobacteria to animalia.
