earticle

영어

Pseudomonas aeruginosa, an opportunistic pathogen controls the production of many exoproteins and secondary metabolites via a hierarchical quorum sensing (QS) mechanism. This highly regulated cascade involves LuxR-like proteins LasR, RhlR and their cognate signal molecules. A third LasR-RhlR homologue, QscR, is a regulator of quorum sensing in P. aeruginosa and plays a role in controlling the virulence. Unlike previously reported LasR and TraR, QS receptor proteins of P. aeruginosa, QscR can be obtained as an apo-protein and can reversibly form an active complex in vitro with its cognate signal molecule, 3-oxododecanoyl-homoserine lactone (3OC12-HSL), and subsequently binds to the target promoter DNA equences. In order to search for potential QS inhibitors, an in vitro gel retardation assay was developed using the purified QscR. The in vitro assay and the in vivo cell-based assay were carried out using QscRoverproducing recombinant strains in screening process. Among >100 furanones tested, three compounds showed strong and dose-dependent inhibitory effects on QscR in both assay systems. One compound in particular, designated as F2, completely inhibited the 3OC12-HSL-dependent QscR activity in vitro at a concentration of 50-fold molar in
excess to 3OC12-HSL. However, a significant decrease in activity was noticed with furanones F3 and F4, which were structurally similar to F2 with a nitro group in place of the amine moiety. These results suggest that (i) the in vitro assay is a sensitive and reliable tool for screening QS inhibitors, and (ii) furanones are potentially important QS inhibitors for many LuxR-type receptor proteins.