Escherichia coli phosphoenolpyruvate dependent phosphotransferase system. NMR studies of the conformation of HPr and P-HPr and the mechanism of energy coupling.

1H and 31P nuclear magnetic resonance investigations of the phosphoprotein intermediate P-HPr and the parent molecule HPr of the E. coli phosphoenolpyruvate dependent phosphotransferase system (PTS) show that HPr can exist in two conformations. These conformations influence the protonation state of the reactive histidine residue, thereby determining the reaction pathway in the phosphoryl group transfer step. A general mechanism is proposed for the energy-coupling process in the PTS.