PHOSPHORYL TRANSFER BETWEEN PHOSPHORYLATED HISTIDINE-CONTAINING PROTEIN AND HISTIDINE-CONTAINING PROTEIN IS NOT AUTOCATALYTIC

Histidine-containing protein, HPr, is a phosphocarrier protein that is part of the bacterial phosphoenolpyruvate:sugar phosphotransferase sy stem. HPr is phosphorylated by enzyme I, and P-HPr transfers the phosp horyl group to the IIA domain of a number of sugar-specific enzyme II complexes. Autocatalytic phosphoryl transfer between P-HPr and HPr has recently been reported [van Dijk, A. A., Eisermann, R., Hengstenberg, W., & Robillard, G. T. (1991) Biochemistry 30, 2876-2882]. Our result s show that this phosphoryl transfer is due to an unidentified contami nant of HPr preparations. The phosphoryl transfer activity is not pres ent in all HPr preparations. When present, the phosphoryl transfer act ivity can be removed by further purification or destroyed over time by resuspension of HPr preparations in water. There is no autocatalytic phosphoryl transfer between P-HPr and HPr.