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.
Pseudomonas aeruginosa uses quorum sensing (QS) as a cell-to-cell communication system to orchestrate the expression of virulence determinants. The biosynthesis of the important Pseudomonas quinolone signal (PQS) requires the pqsABCDE operon. Here, PqsE acts as a pathway-specific thioesterase, but it also contributes to the regulation of bacterial virulence via an unknown mechanism. In this manuscript, we report the discovery of PqsE inhibitors as tool compounds to gain further insights into its different functions. Differential scanning fluorimetry (DSF) was used to screen a fragment library, and isothermal titration calorimetry (ITC) was employed as a secondary filter. As proven by X-ray crystallography, hit molecules bound to the active center inhibiting PqsE's thioesterase activity in cell-based and in vitro assays. Notably, the ligands did not affect the levels of the PqsE-regulated virulence factor pyocyanin. These findings indicate that the regulatory function of PqsE is not linked to its thioesterase activity and must be encoded outside of the active center. This study highlights the potential of fragment-based screening for the discovery of tool compounds. This approach provided novel insight into complex biological systems, which could not be obtained by knockout studies.
Pseudomonas infections. The present work deals with the structure-activity exploration of ureidothiophene-2-carboxylic acids as inhibitors of PqsD, a key enzyme in the biosynthetic pathway of signal molecules in the Pseudomonas QS system. We describe an improvement of the inhibitory activity by successfully combining features from two different PqsD inhibitor classes. Furthermore the functional groups, which are responsible for the inhibitory potency, were identified. Moreover, the inability of the new inhibitors, to prevent signal molecule formation in whole cell assays, is discussed.2
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.