Experimental Data Snapshot

  • Resolution: 1.80 Å
  • R-Value Work: 0.181 
  • R-Value Observed: 0.181 

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Dramatic differences in the binding of UDP-galactose and UDP-glucose to UDP-galactose 4-epimerase from Escherichia coli.

Thoden, J.B.Holden, H.M.

(1998) Biochemistry 37: 11469-11477

  • DOI: https://doi.org/10.1021/bi9808969
  • Primary Citation of Related Structures:  
    1A9Y, 1A9Z

  • PubMed Abstract: 

    UDP-galactose 4-epimerase catalyzes the interconversion of UDP-galactose and UDP-glucose during normal galactose metabolism. Within recent years the enzyme from Escherichia coli has been studied extensively by both biochemical and X-ray crystallographic techniques. One of several key features in the catalytic mechanism of the enzyme involves the putative rotation of a 4'-ketopyranose intermediate within the active site region. The mode of binding of UDP-glucose to epimerase is well understood on the basis of previous high-resolution X-ray crystallographic investigations from this laboratory with an enzyme/NADH/UDP-glucose abortive complex. Attempts to prepare an enzyme/NADH/UDP-galactose abortive complex always failed, however, in that UDP-glucose rather than UDP-galactose was observed binding in the active site. In an effort to prepare an abortive complex with UDP-galactose, a site-directed mutant protein was constructed in which Ser 124 and Tyr 149, known to play critical roles in catalysis, were substituted with alanine and phenylalanine residues, respectively. With this double mutant it was possible to crystallize and solve the three-dimensional structures of reduced epimerase in the presence of UDP-glucose or UDP-galactose to high resolution. This study represents the first direct observation of UDP-galactose binding to epimerase and lends strong structural support for a catalytic mechanism in which there is free rotation of a 4'-ketopyranose intermediate within the active site cleft of the enzyme.

  • Organizational Affiliation

    Department of Biochemistry, University of Wisconsin-Madison 53705, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
UDP-GALACTOSE 4-EPIMERASE338Escherichia coliMutation(s): 2 
Find proteins for P09147 (Escherichia coli (strain K12))
Explore P09147 
Go to UniProtKB:  P09147
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP09147
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.80 Å
  • R-Value Work: 0.181 
  • R-Value Observed: 0.181 
  • Space Group: P 32 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 85α = 90
b = 85β = 90
c = 106.7γ = 120
Software Package:
Software NamePurpose
SAINTdata reduction
XCALIBREdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 1998-10-21
    Type: Initial release
  • Version 1.1: 2008-03-03
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Derived calculations, Version format compliance
  • Version 2.0: 2021-11-03
    Changes: Atomic model, Database references, Derived calculations, Other
  • Version 2.1: 2024-02-07
    Changes: Data collection