Pseudomonas aeruginosa LasR·DNA Binding Is Directly Inhibited by Quorum Sensing Antagonists

Inhibition of quorum sensing in Pseudomonas aeruginosa is of interest as a possible antivirulence strategy for this pathogenic bacterium. The LasR regulator protein is important in coordinating gene expression in response to quorum sensing signaling molecules. One predominant strategy for LasR inhibition is the development of small-molecule antagonists that mimic the native autoinducer, though the mechanism by which they inactivate LasR is not known. This work reveals that multiple antagonists function by binding to and stabilizing LasR in a conformation that renders it unable to bind DNA. Further analysis of purified LasR complexed with known antagonists indicates that DNA binding can be recovered with the addition of native autoinducer, providing insights into the reversibility of ligand binding for this transcription factor. This in vitro assay could be used to assess future promising antagonists and complements existing cell-based reporter assays.