(477g) Engineering a Ligand-Free Molecular Switch In Bacterial Flagellar Motor

E. coli, a well characterized gram-negative bacterium, performs a biased-random walk by rotating its flagella alternately clockwise and counter-clockwise, using tiny reversible electric motors (45 nm dia). Changes in direction of rotation are aided by a molecular switch activated by a signaling molecule (ligand), which allows the bacterium to migrate over relatively large distances in response to attractants or repellents. This phenomenon, known as chemotaxis, is of considerable interest to researchers because it is a model system for understanding the principles of information processing and decision making that control vital functions of living organisms, including motility, gene expression, cytoskeleton dynamics and growth. However, at the heart of chemotaxis in bacteria lies the molecular switch, which is not well understood. The switch enables a change in the direction of rotation of the flagellum, thereby allowing the bacterium to move in a preferred direction. I will discuss our recent efforts on developing a ligand-free molecular switch in the flagellar motor. I will present observations of switching dynamics of this particular switch as well as describe the measurements of protein-turnover of a key component in the switch. These results reveal important aspects of protein sub-unit interactions and are consistent with the notion of stochasticity in conformations in multi-protein complexes.