Journal Article

Structural Basis for Native Agonist and Synthetic Inhibitor Recognition by the Pseudomonas aeruginosa Quorum Sensing Regulator PqsR (MvfR)

Rumbaugh, Kendra, Heeb, Stephan, Fletcher, Matthew, Rampioni, Giordano, Truman, Alex, Pustelny, Christian, Cámara, Miguel, Emsley, Jonas, Ilangovan, Aravindan, Chhabra, Siri Ram, Williams, Paul

2013

Overview

Bacterial populations co-ordinate gene expression collectively through quorum sensing (QS), a cell-to-cell communication mechanism employing diffusible signal molecules. The LysR-type transcriptional regulator (LTTR) protein PqsR (MvfR) is a key component of alkyl-quinolone (AQ)-dependent QS in Pseudomonas aeruginosa. PqsR is activated by 2-alkyl-4-quinolones including the Pseudomonas quinolone signal (PQS; 2-heptyl-3-hydroxy-4(1H)-quinolone), its precursor 2-heptyl-4-hydroxyquinoline (HHQ) and their C9 congeners, 2-nonyl-3-hydroxy-4(1H)-quinolone (C9-PQS) and 2-nonyl-4-hydroxyquinoline (NHQ). These drive the autoinduction of AQ biosynthesis and the up-regulation of key virulence determinants as a function of bacterial population density. Consequently, PqsR constitutes a potential target for novel antibacterial agents which attenuate infection through the blockade of virulence. Here we present the crystal structures of the PqsR co-inducer binding domain (CBD) and a complex with the native agonist NHQ. We show that the structure of the PqsR CBD has an unusually large ligand-binding pocket in which a native AQ agonist is stabilized entirely by hydrophobic interactions. Through a ligand-based design strategy we synthesized and evaluated a series of 50 AQ and novel quinazolinone (QZN) analogues and measured the impact on AQ biosynthesis, virulence gene expression and biofilm development. The simple exchange of two isosteres (OH for NH₂) switches a QZN agonist to an antagonist with a concomitant impact on the induction of bacterial virulence factor production. We also determined the complex crystal structure of a QZN antagonist bound to PqsR revealing a similar orientation in the ligand binding pocket to the native agonist NHQ. This structure represents the first description of an LTTR-antagonist complex. Overall these studies present novel insights into LTTR ligand binding and ligand-based drug design and provide a chemical scaffold for further anti-P. aeruginosa virulence drug development by targeting the AQ receptor PqsR.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Alkylation / Anti-Bacterial Agents - chemistry / Anti-Bacterial Agents - metabolism / Anti-Bacterial Agents - pharmacology / Antimicrobial agents / Bacteria / Bacterial genetics / Bacterial Proteins - agonists / Bacterial Proteins - antagonists & inhibitors / Bacterial Proteins - chemistry / Bacterial Proteins - metabolism / Bacteriology / Binding Sites / Biofilms - drug effects / Biology / Biosynthesis / Chemistry / Drug Design / Gene expression / Gene Expression Regulation, Bacterial / Genetic aspects / Health aspects / Ligands / Materials Science / Medicine / Microbiology / Molecular Conformation / Mutant Proteins - agonists / Mutant Proteins - antagonists & inhibitors / Mutant Proteins - chemistry / Mutant Proteins - metabolism / Nosocomial infections / Peptide Fragments - agonists / Peptide Fragments - antagonists & inhibitors / Peptide Fragments - chemistry / Peptide Fragments - metabolism / Population / Protein Interaction Domains and Motifs / Pseudomonas aeruginosa / Pseudomonas aeruginosa - drug effects / Pseudomonas aeruginosa - pathogenicity / Pseudomonas aeruginosa - physiology / Quinolones - chemistry / Quinolones - metabolism / Quinolones - pharmacology / Quorum sensing / Quorum Sensing - drug effects / Recombinant Proteins - chemistry / Recombinant Proteins - metabolism / Signal Transduction - drug effects / Structure-Activity Relationship / Transcription Factors - agonists / Transcription Factors - antagonists & inhibitors / Transcription Factors - chemistry / Transcription Factors - metabolism / Virulence - drug effects