Quantifying Ligand Binding and Signal Transduction in Escherichia coli Using the Taz Chimera

Abstract

The purpose of this project was to alter the EnvZ signal transduction process in Escherichia coli through replacement of its osmotic sensor with the aspartate binding region of the chemotaxis sensor protein Tar as in Utsumi et al.1 Aspartate binds Tar and signals nonrandom movement of the bacteria toward increasing aspartate concentration. EnvZ is normally an osmotic sensor that activates the protein OmpR. OmpR inactivates the OmpF gene promoter, which produces large membrane pores and it also activates the OmpC gene promoter which produces small membrane pores. Activity of the Tar / EnvZ hybrid, Taz will be determined by measuring light output from bacterial luciferase under control of the OmpC promoter. We hypothesize that light output will be proportional to aspartate concentration. A Tar knockout background will be used to prevent competition with the Taz chimera. This research was funded by NSF award #0966085 provided to Hartwick College and the Hartwick College Chemistry Department. 1Utsumi R, Brissette RE, Rampersaud A, Forst SA, Oosawa K, Inouye M. Activation of bacterial porin gene expression by a chimeric signal. Science. 1989.