POSTERS - BLAST X - University of Utah

BLAST X Poster #41
ELECTROSTATIC EFFECTS ON SIGNALING MUTATIONS IN THE C-TERMINAL REGION
OF THE ESCHERICHIA COLI ASPARTATE CHEMORECEPTOR
Andrew L. Seely, Run-Zhi Lai, and Michael D. Manson, Department of Biology, Texas A&M
University, College Station, TX 77843
The Escherichia coli aspartate chemoreceptor (Tar) responds to attractant by modulating
the rotational bias of the flagellar motor. Previous studies measured the effects on Tar signaling
when positive residues in its extreme C-terminal region were either neutralized or changed to
negative residues. While this region is important as a linker to the NWETF pentapeptide where
methylation and demethylation enzymes bind, it also affects transmembrane signaling. An
R505A substitution decreased the receptor’s ability to respond to aspartate by 40%, and an
R505E charge reversal completely abolished stimulation by aspartate. It was also noted that
R505E may interact with D273 to destabilize the “on” signaling state (Lai, et al, Advanced
Publication in Biochemistry, 2008). We hypothesize that secondary mutations within the
background of the R505 mutations, and an additional R514A/E mutant, can potentially rescue or
exacerbate the ability of mutated Tar to respond to aspartate. Specific mutations will include
D273N/R, D263R, R228A/E, R505D and R509E. We will test our hypothesis in vivo through
chemotaxis swarm assays, receptor methylation assays, and tethered cell assays. Our
hypothesis will also be tested in vitro through CheA-Kinase assays.
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