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 system. HPr is phosphorylated by enzyme I, and P-HPr transfers the phosphoryl 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 results show that this phosphoryl transfer is due to an unidentified contaminant of HPr preparations. The phosphoryl transfer activity is not present in all HPr preparations