Moonlighting chaperone activity of the enzyme PqsE contributes to RhlR-controlled virulence of Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa is a major cause of nosocomial infections and also leads to severe exacerbations in cystic fibrosis or chronic obstructive pulmonary disease. Three intertwined quorum sensing systems control virulence of P. aeruginosa, with the rhl circuit playing the leading role in late and chronic infections. The majority of traits controlled by rhl transcription factor RhlR depend on PqsE, a dispensable thioesterase in Pseudomonas Quinolone Signal (PQS) biosynthesis that interferes with RhlR through an enigmatic mechanism likely involving direct interaction of both proteins. Here we show that PqsE and RhlR form a 2:2 protein complex that, together with RhlR agonist N-butanoyl-L-homoserine lactone (C4-HSL), solubilizes RhlR and thereby renders the otherwise insoluble transcription factor active. We determine crystal structures of the complex and identify residues essential for the interaction. To corroborate the chaperone-like activity of PqsE, we design stability-optimized variants of RhlR that bypass the need for C4-HSL and PqsE in activating PqsE/RhlR-controlled processes of P. aeruginosa. Together, our data provide insight into the unique regulatory role of PqsE and lay groundwork for developing new P. aeruginosa-specific pharmaceuticals.

Inhibition and eradication of Pseudomonas aeruginosa biofilms by secondary metabolites of Nocardiopsis lucentensis EMB25

“…Crystal structure of full-length RhlR bound to N -butanoyl- l -homoserine lactone also became available very recently (PDB: ) which contains 75 mutations. 44 Superimposition of the Alphafold model of the N-terminus domain on the crystal structure yielded rmsd of 1.2 Å indicating high structural similarity. Thus, Alphafold model was used for docking.…”

Pseudomonas aeruginosa strains belonging to phylogroup 3 frequently exhibit an atypical quorum sensing response: the case of MAZ105, a tomato rhizosphere isolate

“…To determine whether other phylogroup 3 strains with a defective PQS QS system were present among the 47 strains analysed (Table S1) we searched for mutations in the pqsABCD sequence in the 30 strains that do not have mutations in pqsR. We found three strains that contain mutations in pqsA: MAZ105 contains a 7 nt deletion (at positions [13][14][15][16][17][18][19]) that causes a frameshift mutation (Fig. 2, Table 2), while LMG5031 and WH-SGI-V-07287 strains have a deletion of 3 nt at positions 382, 383 and 384, causing an in-frame deletion (Table 2).…”

“…This operon encodes the enzymes responsible for HHQ synthesis, and the enzyme PqsH catalyses the conversion of HHQ to PQS. The role of the PQS system in P. aeruginosa QS response is mainly due to the ability of PqsE to stabilize and modulate the transcriptional activity of RhlR, presumably by forming a protein complex [14][15][16]. This is especially apparent in PYO production, since no PYO is produced in a pqsE mutant, even though HHQ and PQS are synthesized [14].…”

Paecilomycone Inhibits Quorum Sensing in Gram-Negative Bacteria

“…PqsBC complex might be a direct target of paecilomycone. PqsE regulates the production of phenazines via RhlR ( 43 – 49 ). A mutant lacking PqsE did not produce PCA or pyocyanin, underlining the importance of PqsE for production of these phenazines.…”