Structure of phosphorylated enzyme I, the phosphoenolpyruvate:sugar phosphotransferase system sugar translocation signal protein

Proc Natl Acad Sci U S A. 2006 Oct 31;103(44):16218-23. doi: 10.1073/pnas.0607587103. Epub 2006 Oct 19.


Bacterial transport of many sugars, coupled to their phosphorylation, is carried out by the phosphoenolpyruvate (PEP):sugar phosphotransferase system and involves five phosphoryl group transfer reactions. Sugar translocation initiates with the Mg(2+)-dependent phosphorylation of enzyme I (EI) by PEP. Crystals of Escherichia coli EI were obtained by mixing the protein with Mg(2+) and PEP, followed by oxalate, an EI inhibitor. The crystal structure reveals a dimeric protein where each subunit comprises three domains: a domain that binds the partner PEP:sugar phosphotransferase system protein, HPr; a domain that carries the phosphorylated histidine residue, His-189; and a PEP-binding domain. The PEP-binding site is occupied by Mg(2+) and oxalate, and the phosphorylated His-189 is in-line for phosphotransfer to/from the ligand. Thus, the structure represents an enzyme intermediate just after phosphotransfer from PEP and before a conformational transition that brings His-189 approximately P in proximity to the phosphoryl group acceptor, His-15 of HPr. A model of this conformational transition is proposed whereby swiveling around an alpha-helical linker disengages the His domain from the PEP-binding domain. Assuming that HPr binds to the HPr-binding domain as observed by NMR spectroscopy of an EI fragment, a rotation around two linker segments orients the His domain relative to the HPr-binding domain so that His-189 approximately P and His-15 are appropriately stationed for an in-line phosphotransfer reaction.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Binding Sites
  • Carbohydrate Metabolism*
  • Crystallization
  • Crystallography, X-Ray
  • Dimerization
  • Escherichia coli / enzymology
  • Histidine / chemistry
  • Histidine / metabolism
  • Models, Molecular
  • Phosphoenolpyruvate / chemistry*
  • Phosphoenolpyruvate / metabolism*
  • Phosphoenolpyruvate Sugar Phosphotransferase System / chemistry*
  • Phosphoenolpyruvate Sugar Phosphotransferase System / metabolism*
  • Phosphorylation
  • Phosphotransferases (Nitrogenous Group Acceptor) / chemistry*
  • Phosphotransferases (Nitrogenous Group Acceptor) / metabolism*
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary


  • Histidine
  • Phosphoenolpyruvate
  • Phosphoenolpyruvate Sugar Phosphotransferase System
  • Phosphotransferases (Nitrogenous Group Acceptor)
  • phosphoenolpyruvate-protein phosphotransferase