HOLOLUXP:LUXQ

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。细胞外信号分子自动诱导物-2(AI-2)介导了不同细菌物种间的群体感应通讯。在海洋弧菌中，AI-2与周质受体LuxP的结合调节内膜传感器蛋白LuxQ的活性，将AI-2信息传递到细胞质中。在低细胞密度时，当LuxP不与AI-2结合时，LuxQ作为一种激酶发挥作用；而在高细胞密度时，当LuxP与AI-2结合时，LuxQ作为一种磷酸酶发挥作用。我们已经证明了哈维氏弧菌LuxP在AI-2存在和不存在的情况下都与LuxQ存在结构性联系。ApoLuxP的1.9°X射线晶体结构与LuxQ的周质结构域结合，表明后者含有两个串联的PAS(PER/Arnt/Simple-Mind)折叠。因此，尽管许多原核生物的PAS折叠本身与配体结合，但LuxQ周质PAS折叠却与LuxP结合，监控其AI-2的占据。破坏apoLuxP：LuxQ界面的突变使哈维氏弧菌对AI-2敏感，这意味着AI-2结合导致一组LuxP：LuxQ触点与另一组触点的替换。这些构象变化在两种相反的酶活性之间切换LuxQ，每一种酶活性都向细胞质传递关于周围环境的细胞密度的信息。比较载脂蛋白复合体和全息复合体的结构将揭示AI-2诱导的构象变化，从而揭示AI-2信号调节的机制。细菌通过一种称为群体感应的机制来调节基因表达，以应对细胞密度的变化。这种密度触发的反应导致细菌种群内的协调表型变化。群体感应指导毒力因子的表达、生物膜的形成、生物发光、抗生素生产和DNA交换等过程。我们的研究将有助于干扰群体感应的广谱抗菌化合物的合理设计。随着细菌越来越多地对目前的抗菌疗法产生抗药性，此类化合物的发现至关重要。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The extracellular signal molecule autoinducer-2 (AI-2) mediates quorum sensing communication in diverse bacterial species. In marine vibrios, binding of AI-2 to the periplasmic receptor LuxP modulates the activity of the inner membrane sensor kinase LuxQ, transducing the AI-2 information into the cytoplasm. At low cell density, when LuxP is not bound to AI-2, LuxQ functions as a kinase, whereas at high cell density, when LuxP is bound to AI-2, LuxQ acts as a phosphatase. We have shown that Vibrio harveyi LuxP associates constitutively with LuxQ in both the presence and absence of AI-2. The 1.9 ¿¿ x-ray crystal structure of apoLuxP, complexed with the periplasmic domain of LuxQ, reveals that the latter contains two tandem PAS (Per/ARNT/Simple-minded) folds. Thus, although many prokaryotic PAS folds themselves bind ligands, the LuxQ periplasmic PAS folds instead bind LuxP, monitoring its AI-2 occupancy. Mutations that disrupt the apoLuxP:LuxQ interface sensitize V. harveyi to AI-2, implying that AI-2 binding causes the replacement of one set of LuxP:LuxQ contacts with another. These conformational changes switch LuxQ between two opposing enzymatic activities, each of which conveys information to the cytoplasm about the cell density of the surrounding environment. Comparison of the apo complex and holo complex (proposed here) structures will reveal AI-2-induced conformational changes, and therefore, the mechanism of AI-2 signaling regulation. Bacteria modulate gene expression in response to changes in cell density via a mechanism termed quorum sensing. This density-triggered response results in coordinated phenotypic changes within bacterial populations. Quorum sensing directs processes including virulence factor expression, biofilm development, bioluminescence, antibiotic production, and DNA exchange. Our studies will facilitate the rational design of broad-spectrum antibacterial compounds that interfere with quorum sensing. Discovery of such compounds is critical as bacteria increasingly become resistant to current antimicrobial therapies.