1 Department of Electrical Engineering, Technical University of Denmark2 Biomedical Engineering, Department of Electrical Engineering, Technical University of Denmark3 Department of Systems Biology, Technical University of Denmark4 Center for Biological Sequence Analysis, Department of Systems Biology, Technical University of Denmark5 Department of Chemistry, Technical University of Denmark6 University of Copenhagen7 University of Cambridge8 Copenhagen Center for Health Technology, Center, Technical University of Denmark
We propose a kinetic model for the activation of the las regulon in the opportunistic pathogen Pseudomonas aeruginosa. The model is based on in vitro data and accounts for the LasR dimerization and consecutive activation by binding of two OdDHL signal molecules. Experimentally, the production of the active LasR quorum-sensing regulator was studied in an Escherichia coli background as a function of signal molecule concentration. The functional activity of the regulator was monitored via a GFP reporter fusion to lasB expressed from the native lasB promoter. The new data shows that the active form of the LasR dimer binds two signal molecules cooperatively and that the timescale for reaching saturation is independent of the signal molecule concentration. This favors a picture where the dimerized regulator is protected against proteases and remains protected as it is activated through binding of two successive signal molecules. In absence of signal molecules, the dimerized regulator can dissociate and degrade through proteolytic turnover of the monomer. This resolves the apparent contradiction between our data and recent reports that the fully protected dimer is able to “degrade” when the induction of LasR ceases.
International Journal of Molecular Sciences (online), 2013, Vol 14, Issue 7, p. 13360-13376
Chemistry; Quorum sensing; LasR; Pseudomonas aeruginosa; OdDHL; C12-HSL; Signal molecule; Ligand