Kinetic Model for Signal Binding to the Quorum Sensing Regulator LasR

Anetta Claussen, Tim Holm Jakobsen, Thomas Bjarnsholt, Michael Givskov, Martin Welch, Jesper Ferkinghoff-Borg, Thomas Sams

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    Abstract

    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.
    Original languageEnglish
    JournalInternational Journal of Molecular Sciences (Online)
    Volume14
    Issue number7
    Pages (from-to)13360-13376
    ISSN1661-6596
    DOIs
    Publication statusPublished - 2013

    Keywords

    • Chemistry
    • Quorum sensing
    • LasR
    • Pseudomonas aeruginosa
    • OdDHL
    • C12-HSL
    • Signal molecule
    • Ligand

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