Dual Recognition of the Bacterial Chemoreceptor by

Adaptation to persisting stimulation is required for highly sensitive detection of temporal changes of stim-uli, and often involves covalent modification of recep-tors. Therefore, it is of vital importance to understand how a receptor and its cognate modifying enzyme(s) modulate each other through specific protein-protein interactions. In the chemotaxis of Escherichia coli, adaptation requires methylation of chemoreceptors (e.g. Tar) catalyzed by the CheR methyltransferase. CheR binds to the C-terminal NWETF sequence of a chemore-ceptor that is distinct from the methylation sites. How-ever, little is known about how CheR recognizes its methylation sites or how it is distributed in a cell. In this study, we used comparative genomics to demonstrate that the CheR chemotaxis methyltransferase contain