Sensory transduction in bacterial chemotaxis involves phosphotransfer between Che proteins.

The CheA protein of the Salmonella typhimurium chemotaxis system is phosphorylated by ATP. Phospho-CheA transfers its phosphoryl group to a second chemotaxis protein, CheY. Unlike phospho-CheA, phospho-CheY is relatively unstable, rapidly decaying to phosphate and CheY. We propose that phosphorylation of CheY may play a role in its function as a tumble regulator to control motor behavior in response to attractant and repellent stimuli.