Investigation of transphosphorylation between chemotaxis proteins and the phosphoenolpyruvate: sugar phosphotransferase system

Transphosphorylation between the chemotaxis proteins and phosphoenolpyruvate:sugar phosphotransferase system (PTS) from Escherichia coli was investigated by incubating the CheA, CheW and CheY proteins of the chemotaxis cascade, and Enzyme I, HPr and Enzyme II^mtl of the PTS with [γ-³²P]ATP or [³²P]phosphoenolpyruvate in the presence and absence of cell extract. In the absence of cell extract, ATP phosphorylated CheA, but in the presence of cell extract, Enzyme I was also phosphorylated. Phosphoenolpyruvate phosphorylated only PTS components. The transphosphorylation of Enzyme I by ATP did not require chemotaxis proteins, and likely occurred through acetate kinase. Regardless of phosphorylation state, the HPr protein did not inhibit the rate of ATP-dependent phosphorylation of the CheA or the CheY protein. It is concluded that chemotaxis to PTS substrates is not mediated by transphosphorylation between the PTS and chemotaxis systems.