Dioxygenase-Mediated Quenching of Quinolone-Dependent Quorum Sensing in Pseudomonas aeruginosa

School of Molecular Medical Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK.
Chemistry & biology (Impact Factor: 6.65). 12/2009; 16(12):1259-67. DOI: 10.1016/j.chembiol.2009.11.013
Source: PubMed


2-Heptyl-3-hydroxy-4(1H)-quinolone (PQS) is a quorum-sensing signal molecule used by Pseudomonas aeruginosa. The structural similarity between 3-hydroxy-2-methyl-4(1H)-quinolone, the natural substrate for the 2,4-dioxygenase, Hod, and PQS prompted us to investigate whether Hod quenched PQS signaling. Hod is capable of catalyzing the conversion of PQS to N-octanoylanthranilic acid and carbon monoxide. In P. aeruginosa PAO1 cultures, exogenously supplied Hod protein reduced expression of the PQS biosynthetic gene pqsA, expression of the PQS-regulated virulence determinants lectin A, pyocyanin, and rhamnolipids, and virulence in planta. However, the proteolytic cleavage of Hod by extracellular proteases, competitive inhibition by the PQS precursor 2-heptyl-4(1H)-quinolone, and PQS binding to rhamnolipids reduced the efficiency of Hod as a quorum-quenching agent. Nevertheless, these data indicate that enzyme-mediated PQS inactivation has potential as an antivirulence strategy against P. aeruginosa.

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Available from: Paul Williams, Nov 20, 2014
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    • "The organic products of the reactions catalyzed by HodC and HodC-W160A were prepared by chromatography as described previously (Pustelny et al., 2009) and identified by HPLC and mass spectrometry. The possibility of formate formation in a side reaction was assessed with formate dehydrogenase (see the Supplemental Experimental Procedures for details). "
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    ABSTRACT: In contrast to the majority of O2-activating enzymes, which depend on an organic cofactor or a metal ion for catalysis, a particular group of structurally unrelated oxygenases is functional without any cofactor. In this study, we characterized the mechanism of O2 activation in the reaction pathway of a cofactor-independent dioxygenase with an α/β-hydrolase fold, which catalyzes the oxygenolytic cleavage of 2-alkyl-3-hydroxy-4(1H)-quinolones. Chemical analysis and electron paramagnetic resonance spectroscopic data revealed that O2 activation in the enzyme's active site is substrate-assisted, relying on single electron transfer from the bound substrate anion to O2 to form a radical pair, which recombines to a C2-peroxide intermediate. Thus, an oxygenase can function without a cofactor, if the organic substrate itself, after activation to a (carb)anion by an active-site base, is intrinsically reactive toward molecular oxygen.
    Preview · Article · Dec 2013 · Chemistry & biology
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    • "The intermediates 1H-4-oxoquinaldine and 1H-3-hydroxy-4-oxoquinaldine of the pathway are structural analogs of the quorum sensing signaling molecules HHQ (2-heptyl-4(1H)-quinolone) and PQS (2-heptyl-3-hydroxy-4(1H)-quinolone) of Pseudomonas aeruginosa. The enzymes 1H-4-oxoquinaldine 3-monooxygenase and 1H-3-hydroxy-4-oxoquinaldine 2,4-dioxygenase from strain Rue61a are indeed capable of catalyzing the hydroxylation of HHQ to PQS (unpublished data) and the cleavage of PQS [75], respectively. However, the catalytic activities of the monooxygenase and the 2,4-dioxygenase towards these signaling molecules are much lower than towards the physiological substrates, supporting the notion that the proteins have not evolved to act as a quorum quenching enzymes, but have a catabolic role. "
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    • "The quorum quenching of specific virulence factors observed in laboratory cultures could be extended to a plant infection model where Hod reduced both virulence and bacterial growth of P. aeruginosa in leaf tissues. These findings highlight the potential of quenching alkylquinolone-dependent quorum sensing and hence virulence through the enzymatic degradation of alkylquinolone signaling molecules (Pustelny et al. 2009). Like Renilla luciferase, Hod and Qdo are monomeric proteins belonging to the α/β-hydrolase fold family (Fischer et al. 1999; Fischer and Fetzner 2000; Steiner et al. 2010). "
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