dissertationThe chemotaxis signaling pathway of Escherichia coli is the best studied signal transduction mechanism in biology. Better understanding of this signal-processing machinery at the molecular level will foster new therapies for pathogenic infections and new designs of highly specific and sensitive biosensors. A sensory adaptation system plays a critical role in this chemotactic behavior. Sensory adaptation is regulated by covalent modifications of the chemoreceptors, mediated by CheR and CheB enzymes. This PhD research project explores the sensory adaptation mechanism of the serine receptor (Tsr) in E. coli. In this study, I showed that all adaptation sites of Tsr, including the fifth unorthodox site, worked in a similar way to regulate Tsr signal output. I also found that site 5 (Tsr-E502) and site 3 (Tsr-Q311) have differential signaling effects, mainly due to their different localizations on the methylation helices. Finally, I discovered unexpected signaling effects of CheR and CheB, the two adaptation enzymes. In summary, this thesis provides important insights into the sensory adaptation system and receptor input-output control in bacterial chemotaxis
