An Integrative Analysis of Two-Component Signal Transduction from the Structural to Systems Level
Whether residing in a freshwater stream or an animal host during infection, the survival of bacterial cells depends on reliable detection and adaptation to changes in their physical and chemical microenvironment. A primary means of such regulation involvesthe coordinate action of sensor histidine kinases and their cognate response regulators. Together, these proteins form two-component signal transduction systems (TCS), which typically regulate gene expression in response to the presence (or absence) of some cellular or environmental signal. While thousands of TCS proteins have been annotated in sequenced bacterial genomes, very little is known about the nature of signals that regulate TCS function. To identify TCS signals, I have developed a structure-based bioinformatic method to predict cofactor binding histidine kinases. Working in the model bacterium, Caulobacter crescentus, this method has provided an entry point to signal identification and enabled, for the first time, a functiuonal definition of a limited number of TCS signals in Caulobacter. In an effort to further expand our view of the physical and chemical signaling space of this model microbe, we propose to use a conditional screen based on growth of two-component gene deletion strains in chemically-defined medium. We have already identified 180 unique medium conditions that support the growth of Caulobacter and will grow a set of bar-coded histidine kinase and response regulator gene deletion strains that exhibit defects in yield or growth kinetics under specific medium conditions will be measured using Affymetrix gene chips. The topology of TCS ntetworks for which we identify functional signals will then be iteratively refined via a combination of genetic analysis, experimental biochemical measurements and computer simulations of transcriptional input/output behavior in response to signal dosage. Focusing on a flavin-binding, photosensory histidine kinase activation upon detection of an environmental signal(in this case, photons). The experiments proposed her promise to lead to a more integrated understanding of the molecular mechanism, function, and network structure of this important class of cellular signaling systems.
Arnold O. Beckman exemplifies the meaning of the word humanitarian. Combined with his unwavering enthusiasm for life, his keen sense of humor and his strong moral and ethical principles, he is a national icon.