HPr is a protein that carries phosphate groups that is essential to a very important system called the PTS (phosphotransferase system). The PTS is a major carbohydrate transport system that is present in many bacteria and involves enzymes in the membranes and cytoplasm that catalyze the phosphorylation (adding of a phosphate group) of incoming sugar substrates and moves them across the cell membrane to HPr. HPr is needed to accept the phosphorylated sugar substrate group, and thereby regulates the sugar transport in the PTS. A normally functioning PTS carries out numerous regulatory functions; without it functioning normally, the proteins that might interact or cascade with another protein may not be able to do so. A normally functioning PTS moves substrates to the right place for it to bind to the correct enzyme, which may be interrupted by an abnormally functioning PTS.

HPr has been observed to play an important role in interacting with several different functions and pathways, but may or may not have been instrumental in regulating many processes. As E. coli is a well-known bacterium, the protein-protein interactions and activity with HPr or HPr-P (when HPr has been phosphorylated) are observed and measured through Rodionova et. al (2017). The interaction between E. coli proteins and HPr show how HPr or HPr-P could be interacting with several other bacteria with the same chemical structure and organelles that E. coli possesses. The interactions presented throughout Rodionova et. al (2017) show how HPr or HPr-P have a role in the activity of PykF, PfkB, NagB, and Adk, which are core proteins in E. coli.

• Abstract
• Introduction
• Experiments
  • Allosteric activation of PykF by HPr
  • Allosteric activation of PfkB by HPr
  • Allosteric activation of NagB by HPr
  • Inhibition of ATP-dependent Adk by HPr-P
• Implications
  • Protein-Protein Interactions
• Support pages
  • Coupled Assays