Azotobacter vinelandii Mannuronan C-5 epimerase AlgE4 A-module

Experimental Data Snapshot

  • Resolution: 2.10 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.194 

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Structural and Mutational Characterization of the Catalytic A-module of the Mannuronan C-5-epimerase AlgE4 from Azotobacter vinelandii.

Rozeboom, H.J.Bjerkan, T.M.Kalk, K.H.Ertesvag, H.Holtan, S.Aachmann, F.L.Valla, S.Dijkstra, B.W.

(2008) J Biol Chem 283: 23819-23828

  • DOI: https://doi.org/10.1074/jbc.M804119200
  • Primary Citation of Related Structures:  
    2PYG, 2PYH

  • PubMed Abstract: 

    Alginate is a family of linear copolymers of (1-->4)-linked beta-d-mannuronic acid and its C-5 epimer alpha-l-guluronic acid. The polymer is first produced as polymannuronic acid and the guluronic acid residues are then introduced at the polymer level by mannuronan C-5-epimerases. The structure of the catalytic A-module of the Azotobacter vinelandii mannuronan C-5-epimerase AlgE4 has been determined by x-ray crystallography at 2.1-A resolution. AlgE4A folds into a right-handed parallel beta-helix structure originally found in pectate lyase C and subsequently in several polysaccharide lyases and hydrolases. The beta-helix is composed of four parallel beta-sheets, comprising 12 complete turns, and has an amphipathic alpha-helix near the N terminus. The catalytic site is positioned in a positively charged cleft formed by loops extending from the surface encompassing Asp(152), an amino acid previously shown to be important for the reaction. Site-directed mutagenesis further implicates Tyr(149), His(154), and Asp(178) as being essential for activity. Tyr(149) probably acts as the proton acceptor, whereas His(154) is the proton donor in the epimerization reaction.

  • Organizational Affiliation

    Laboratory of Biophysical Chemistry, GBB, University of Groningen, Nijenborgh 4, Groningen, The Netherlands.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Poly(beta-D-mannuronate) C5 epimerase 4
A, B
377Azotobacter vinelandiiMutation(s): 0 
Gene Names: algE4
EC: 5.1.3
Find proteins for Q44493 (Azotobacter vinelandii)
Explore Q44493 
Go to UniProtKB:  Q44493
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ44493
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 2.10 Å
  • R-Value Free: 0.235 
  • R-Value Work: 0.194 
  • Space Group: P 21 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 173.953α = 90
b = 121.346β = 90
c = 44.715γ = 90
Software Package:
Software NamePurpose
PDB_EXTRACTdata extraction
DENZOdata reduction
SCALEPACKdata scaling

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2008-05-27
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Non-polymer description, Version format compliance
  • Version 1.2: 2024-02-21
    Changes: Data collection, Database references, Derived calculations