Phosphocarrier protein

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Phosphotransferase system, phosphocarrier HPr protein
Phosphocarrier protein HPr, E.Coli
Available protein structures:
Pfam  structures / ECOD  
PDBsumstructure summary
PDB1cm2​, 1cm3​, 1fu0​, 1ggr​, 1hdn​, 1j6t​, 1jem​, 1k1c​, 1ka5​, 1kkl

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

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 Gram-positive bacteria only, is phosphorylated by an ATP-dependent protein kinase, a process which probably plays a regulatory role in sugar transport.


  1. ^ Postma PW, Lengeler JW, Jacobson GR (1993). "Phosphoenolpyruvate:carbohydrate phosphotransferase systems of bacteria". Microbiol. Rev. 57 (3): 543–594. doi:10.1128/MMBR.57.3.543-594.1993. PMC 372926. PMID 8246840.
  2. ^ Meadow ND, Fox DK, Roseman S (1990). "The bacterial phosphoenolpyruvate: glycose phosphotransferase system". Annu. Rev. Biochem. 59 (1): 497–542. doi:10.1146/ PMID 2197982.
  3. ^ Boelens R, Scheek RM, Robillard GT, van Nuland NA (1995). "High-resolution structure of the phosphorylated form of the histidine-containing phosphocarrier protein HPr from Escherichia coli determined by restrained molecular dynamics from NMR-NOE data". J. Mol. Biol. 246 (1): 180–193. doi:10.1006/jmbi.1994.0075. PMID 7853396.
  4. ^ Liao DI, Herzberg O (1994). "Refined structures of the active Ser83→Cys and impaired Ser46→Asp histidine-containing phosphocarrier proteins". Structure. 2 (12): 1203–1216. doi:10.1016/S0969-2126(94)00122-7. PMID 7704530.
This article incorporates text from the public domain Pfam and InterPro: IPR000032