Mutational Replacements at the “Glycine Hinge” of the Escherichia coli Chemoreceptor Tsr Support a Signaling Role for the C-Helix Residue

Bacterial chemoreceptors are dimeric membrane proteins that transmit signals from a periplasmic ligand-binding domain to the interior of the cells. The highly conserved cytoplasmic domain consists of a long hairpin that in the dimer forms a four-helix coiled-coil bundle. The central region of the bundle couples changes in helix packing that occur in the membrane proximal region to the signaling tip, controlling the activity of an associated...