Histidine-phosphorylatable phosphocarrier protein (HPr) is essential in the PTS (phosphotransferase system), which transports sugar in many bacteria. While it has been found that HPr interacts with several carbohydrate-metabolizing enzymes, this study provides evidence that HPr interacts with several E. Coli (Escherichia coli) bacteria proteins. This is demonstrated through four different experiments that depend on the presence or the absence of HPr or HPr-P: allosteric regulation on PykF (pyruvate kinase) activity, PfkB (phosphofructokinase) activity, NagB (glucosamine-6-phosphate deaminase) activity, and Adk (adenylate kinase) activity. Both HPr and HPr-P (when HPr is phosphorylated) are tested with each experiment, and measured through steady-state kinetics.

The steady state kinetics are expressed through graphs and tables for each experiment. HPr was allosterically regulated through coupled assays and showed activity with PykF, PfkB, and NagB; HPr-P was allosterically inhibited through a coupled assay and showed inhibition with Adk. These assays showed HPr and HPr-P directly interacting with E.coli proteins and regulating or inhibiting protein activity.