Claussen Anetta, Jakobsen Tim Holm, Bjarnsholt Thomas, Givskov Michael, Welch Martin, Ferkinghoff-Borg Jesper, Sams Thomas
Biomedical Engineering, Department of Electrical Engineering, Ørsteds Plads 349, Technical University of Denmark, Kongens Lyngby DK-2800, Denmark.
Int J Mol Sci. 2013 Jun 27;14(7):13360-76. doi: 10.3390/ijms140713360.
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.
我们提出了一种用于激活机会致病菌铜绿假单胞菌中las操纵子的动力学模型。该模型基于体外数据，考虑了LasR二聚化以及两个OdDHL信号分子结合导致的连续激活。通过实验，在大肠杆菌背景下研究了活性LasR群体感应调节因子的产生与信号分子浓度的关系。通过与源自天然lasB启动子表达的lasB融合的GFP报告基因监测调节因子的功能活性。新数据表明，LasR二聚体的活性形式协同结合两个信号分子，达到饱和的时间尺度与信号分子浓度无关。这支持了一种情况，即二聚化的调节因子受到蛋白酶的保护，并在通过结合两个连续信号分子被激活时保持受保护状态。在没有信号分子的情况下，二聚化的调节因子可以通过单体的蛋白水解周转而解离和降解。这解决了我们的数据与最近报道之间的明显矛盾，即当LasR的诱导停止时，完全受保护的二聚体能够“降解”。
