Reversible Signal Binding by the Pseudomonas aeruginosa Quorum-Sensing Signal Receptor LasR

Abstract

Many members of the LuxR family of acyl-homoserine lactone (acyl-HSL)-dependent quorum-sensing transcriptional activators are thought to have the unusual characteristics of requiring the signal ligand during polypeptide synthesis to fold into an active conformation and of binding signal extraordinarily tightly. This is the case for the N-3-oxo-dodecanoyl-HSL-dependent Pseudomonas aeruginosa virulence regulator LasR. We present evidence that LasR can fold into an active conformation in vivo in the absence of the acyl-HSL ligand. We also present evidence indicating that in the cellular environment, LasR and N-3-oxo-dodecanoyl-HSL readily dissociate. After dissociation, LasR can remain in a properly folded conformation capable of reassociating with signal. We present a new model for the folding and signal binding of LasR and other members of the family of transcription factors to which LasR belongs. Our findings have important implications concerning the cellular responses to decreased environmental concentrations of signals and have implications about potential quorum-sensing inhibition strategies.

The role of BST‐2/Tetherin in host protection and disease manifestation

“…Experimental evidence suggest that Vpu does not affect BST‐2 internalization, but rather prevents proper intracellular transportation of newly synthesized BST‐2 from the ER and TGN to the cell membrane 89, 90 (Fig. 2 #5) and/or from early endosomes to the cell surface 44, 88, 91 (Fig. 2 #6).…”

“…2 #6). Vpu‐mediated inhibition of BST‐2 anterograde transport occurs in the absence of Ser52 and Ser56 phosphorylation 89, 90, 91.…”

Mutational Analysis of the Quorum-Sensing Receptor LasR Reveals Interactions that Govern Activation and Inhibition by Nonlactone Ligands

“…A typical LuxR-type protein is LasR from the opportunistic pathogen Pseudomonas aeruginosa . When its cognate signal AHL ( N -(3-oxo)-dodecanoyl L-homoserine lactone, OdDHL, Figure 1) is present at a quorate concentration, LasR binds this signal and is stabilized by it in an active, dimerized form that recognizes certain promoters and recruits transcriptional machinery to induce QS gene expression (Sappington et al, 2011). …”

Transcriptional regulation of Pseudomonas aeruginosa rhlR: role of the CRP orthologue Vfr (virulence factor regulator) and quorum-sensing regulators LasR and RhlR

“…In this experiment (Table 3) we used as positive control the DNA sequence of the lasI las box that is specifically bound by LasR/3O-C12-HSL (Schuster et al, 2004), and as negative control for LasR/3-O-C12-HSL binding and control of binding specificity we used the las box of rhlA that is only bound by RhlR in both the presence and absence of C4-HSL (in the first case it activates transcription, while in the second one it acts as a repressor: Medina et al, 2003b). It has been recently reported that some structural characteristics of LasR that affect its capacity to reversibly bind 3-O-C12-HSL, and ultimately to bind las boxes, are not maintained in the purified protein (Sappington et al, 2011). Thus it is preferable to use in vivo systems to determine LasR DNAbinding specificity rather than in vitro systems such as electrophoretic mobility shift assays.…”