Phosphocarrier protein

Histidine-containing phosphocarrier protein (HPr) is a small cytoplasmic protein that is a component of the phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS).^[1][2]

Phosphotransferase system, phosphocarrier HPr protein
Phosphocarrier protein HPr, E. coli
Identifiers
Symbol	PTS_HPr_protein
Pfam	PF00381
InterPro	IPR000032
PROSITE	PDOC00318
SCOP2	1ptf / SCOPe / SUPFAM
Available protein structures: Pfam   structures / ECOD   PDB RCSB PDB; PDBe; PDBj PDBsum structure summary PDB 1cm2​, 1cm3​, 1fu0​, 1ggr​, 1hdn​, 1j6t​, 1jem​, 1k1c​, 1ka5​, 1kkl​

The phosphoenolpyruvate-dependent sugar phosphotransferase system (PTS) is a major carbohydrate transport system in bacteria. The PTS catalyses the phosphorylation of sugar substrates during their translocation across the cell membrane. The mechanism involves the transfer of a phosphoryl group from phosphoenolpyruvate (PEP) via enzyme I (EI) to enzyme II (EII) of the PTS system, which in turn transfers it to a phosphocarrier protein (HPr).^[3][4] In some bacteria HPr is a domain in a larger protein that includes an EIII(Fru) (IIA) domain and in some cases also an EI domain.

There is a conserved histidine in the N-terminus of HPr, which serves as an acceptor for the phosphoryl group of EI. In the central part of HPr there is a conserved serine which, in most Gram-positive bacteria and certain Gram-negative bacteria, is phosphorylated by an ATP-dependent protein kinase, a process which probably plays a regulatory role in sugar transport.^[5]