Crystal structure of apo human galactose mutarotase

Experimental Data Snapshot

  • Resolution: 2.20 Å
  • R-Value Free: 0.201 
  • R-Value Work: 0.172 
  • R-Value Observed: 0.174 

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This is version 1.4 of the entry. See complete history


Molecular structure of human galactose mutarotase

Thoden, J.B.Timson, D.J.Reece, R.J.Holden, H.M.

(2004) J Biol Chem 279: 23431-23437

  • DOI: https://doi.org/10.1074/jbc.M402347200
  • Primary Citation of Related Structures:  
    1SNZ, 1SO0

  • PubMed Abstract: 

    Galactose mutarotase catalyzes the conversion of beta-d-galactose to alpha-d-galactose during normal galactose metabolism. The enzyme has been isolated from bacteria, plants, and animals and is present in the cytoplasm of most cells. Here we report the x-ray crystallographic analysis of human galactose mutarotase both in the apoform and complexed with its substrate, beta-d-galactose. The polypeptide chain folds into an intricate array of 29 beta-strands, 25 classical reverse turns, and 2 small alpha-helices. There are two cis-peptide bonds at Arg-78 and Pro-103. The sugar ligand sits in a shallow cleft and is surrounded by Asn-81, Arg-82, His-107, His-176, Asp-243, Gln-279, and Glu-307. Both the side chains of Glu-307 and His-176 are in the proper location to act as a catalytic base and a catalytic acid, respectively. These residues are absolutely conserved among galactose mutarotases. To date, x-ray models for three mutarotases have now been reported, namely that described here and those from Lactococcus lactis and Caenorhabditis elegans. The molecular architectures of these enzymes differ primarily in the loop regions connecting the first two beta-strands. In the human protein, there are six extra residues in the loop compared with the bacterial protein for an approximate longer length of 9 A. In the C. elegans protein, the first 17 residues are missing, thereby reducing the total number of beta-strands by one.

  • Organizational Affiliation

    Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
aldose 1-epimerase
A, B
344Homo sapiensMutation(s): 0 
Gene Names: GALMBLOCK25
UniProt & NIH Common Fund Data Resources
Find proteins for Q96C23 (Homo sapiens)
Explore Q96C23 
Go to UniProtKB:  Q96C23
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ96C23
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.20 Å
  • R-Value Free: 0.201 
  • R-Value Work: 0.172 
  • R-Value Observed: 0.174 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 60.7α = 90
b = 90.7β = 102.5
c = 70γ = 90
Software Package:
Software NamePurpose
FRAMBOdata collection
XDSdata reduction
XDSdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-03-30
    Type: Initial release
  • Version 1.1: 2008-04-29
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-10-11
    Changes: Refinement description
  • Version 1.4: 2023-08-23
    Changes: Data collection, Database references, Refinement description