Crystal structure of HpcG complexed with Mg ion

Experimental Data Snapshot

  • Resolution: 1.69 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.195 

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This is version 1.3 of the entry. See complete history


Structure and Mechanism of HpcG, a Hydratase in the Homoprotocatechuate Degradation Pathway of Escherichia coli

Izumi, A.Rea, D.Adachi, T.Unzai, S.Park, S.Y.Roper, D.I.Tame, J.R.H.

(2007) J Mol Biol 370: 899-911

  • DOI: https://doi.org/10.1016/j.jmb.2007.05.006
  • Primary Citation of Related Structures:  
    2EB4, 2EB5, 2EB6

  • PubMed Abstract: 

    HpcG catalyses the hydration of a carbon-carbon double bond without the aid of any cofactor other than a simple divalent metal ion such as Mg(2+). Since the substrate has a nearby carbonyl group, it is believed that it first isomerises to form a pair of conjugated double bonds in the enol tautomer before Michael addition of water. Previous chemical studies of the reaction, and that of the related enzyme MhpD, have failed to provide a clear picture of the mechanism. The substrate itself is unstable, preventing co-crystallisation or soaking of crystals, but oxalate is a strong competitive inhibitor. We have solved the crystal structure of the protein in the apo form, and with magnesium and oxalate bound. Modelling substrate into the active site suggests the attacking water molecule is not part of the metal coordination shell, in contrast to a previous proposal. Our model suggests that geometrically strained cis isomer intermediates do not lie on the reaction pathway, and that separate groups are involved in the isomerisation and hydration steps.

  • Organizational Affiliation

    Protein Design Laboratory, Yokohama City University, Suehiro 1-7-29, Tsurumi, Yokohama 230-0045, Japan.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
2-oxo-hept-3-ene-1,7-dioate hydratase
A, B, C, D, E
267Escherichia coliMutation(s): 0 
Gene Names: HPCG
EC: 4.2.1
Find proteins for Q46982 (Escherichia coli)
Explore Q46982 
Go to UniProtKB:  Q46982
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ46982
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.69 Å
  • R-Value Free: 0.213 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.195 
  • Space Group: P 43 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 135.955α = 90
b = 135.955β = 90
c = 194.064γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2007-07-17
    Type: Initial release
  • Version 1.1: 2008-04-30
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance
  • Version 1.3: 2023-10-25
    Changes: Data collection, Database references, Derived calculations, Refinement description