The serine chemoreceptor from Escherichia coli is methylated through an inter-dimer process.

Covalent modification of receptors is a widespread phenomenon in signal transduction. In the chemosensory system of Escherichia coli, the reversible methylation of certain glutamic acid residues in the cytoplasmic domain of receptor homodimers mediates adaptation to stimuli. Here we report that the serine receptor is methylated by an inter-dimer process. Methyltransferase bound to one subunit in a serine receptor homodimer was found to catalyze the addition of methyl groups to a receptor subunit in an adjacent dimer in the membrane. These results demonstrate a role for inter-dimer interactions in transmembrane signaling.