Interaction of sugar transporters and signalling proteins in E. coli chemotaxis
Biophysics
Final Report Abstract
Despite the wealth of knowledge available for many individual cellular components, how these components interact with each other in complex networks to mediate cellular functions remains enigmatic in most cases, even for model organisms such as the gut bacterium Escherichia coli. We investigated cellular function of the phosphotransferase system (PTS), which plays a pivotal role in the uptake of multiple sugars in E. coli and in many other bacteria, and the connection of PTS to another highly conserved cellular network, the chemotaxis system. We used an assay based on Förster (fluorescence) resonance energy transfer (FRET) to quantify directly in the cell the dynamics of protein interactions and to gain insights into signal processing within both networks. We could demonstrate that the PTS network operates as an integral sensor of sugar influx into the cell and transmits this information linearly to regulate other cellular functions, including chemotaxis system and control of the production of second messenger cAMP. Furthermore, we clarified how PTS- mediated stimuli become integrated with conventional chemoreceptor-mediated stimuli within the chemotaxis pathway to elicit a coordinated behavioral response. Surprisingly, we further observed that default influx through the PTS system correlates with the metabolic value of the sugar, which apparently represents an optimal regulatory strategy evolved by bacteria. All of this establishes a new and appealingly simple paradigm for the function of this common bacterial transport and regulatory system.
