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Structural basis for native agonist and synthetic inhibitor recognition by the Pseudomonas aeruginosa quorum sensing regulator PqsR (MvfR)

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

Authors

Aravindan Ilangovan

Matthew Fletcher

Giordano Rampioni

Christian Pustelny

Kendra Rumbaugh

Stephan Heeb

Miguel Cámara

Alex Truman

Siri Ram Chhabra

Jonas Emsley

Paul Williams

Abstract

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.

Journal Article Type Article
Publication Date Jul 25, 2013
Journal PLoS Pathogens
Print ISSN 1553-7366
Electronic ISSN 1553-7366
Publisher Public Library of Science
Peer Reviewed Peer Reviewed
Volume 9
Issue 7
Article Number e1003508
Institution Citation Ilangovan, A., Fletcher, M., Rampioni, G., Pustelny, C., Rumbaugh, K., Heeb, S., …Williams, P. (2013). Structural basis for native agonist and synthetic inhibitor recognition by the Pseudomonas aeruginosa quorum sensing regulator PqsR (MvfR). PLoS Pathogens, 9(7), doi:10.1371/journal.ppat.1003508
DOI https://doi.org/10.1371/journal.ppat.1003508
Publisher URL http://www.plospathogens.org/article/info%3Adoi%2F10.1371%2Fjournal.ppat.1003508
Copyright Statement Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://creativecommons.org/licenses/by/4.0




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