PqsR

PqsR, also known as MvfR (multivirulence factor regulator), is a transcriptional regulator in the bacterium Pseudomonas aeruginosa. It is a key component of the Pseudomonas quinolone signal (PQS) quorum-sensing system and is typically described as a regulator belonging to the LysR-type transcriptional regulator family. PqsR responds to the quorum-sensing molecule PQS by binding to promoter regions to control gene expression.

The primary role of PqsR is to activate transcription of the pqsABCDE operon in the presence of PQS. Activation of this operon enhances production of PQS and related quinolones, which in turn sustain PQS signaling in a positive feedback loop. Through this regulatory circuit, PqsR influences the synthesis of virulence-associated metabolites such as alkyl-quinolones and phenazines, including pyocyanin, as well as factors involved in biofilm formation and overall virulence. The PqsR regulon can intersect with other quorum-sensing systems, coordinating a broader network of gene expression linked to pathogenicity.

Biological and clinical relevance is tied to PqsR’s central role in virulence. Strains lacking functional PqsR often show reduced pyocyanin production and attenuated virulence in infection models, making the PQS-PqsR system a target of interest for anti-virulence strategies. Researchers have investigated inhibitors that block PQS binding to PqsR with the aim of dampening virulence without exerting bactericidal pressure, which could mitigate selective pressures for resistance.

Discovery and naming reflect its function: MvfR highlights its regulatory influence over multiple virulence factors, while PqsR denotes its role in the PQS regulatory pathway.