Binding sub-site dissection of a family 6 carbohydrate-binding module by X-ray crystallography and isothermal titration calorimetry

Experimental Data Snapshot

  • Resolution: 1.69 Å
  • R-Value Free: 0.177 
  • R-Value Work: 0.132 
  • R-Value Observed: 0.134 

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Binding Sub-Site Dissection of a Carbohydrate-Binding Module Reveals the Contribution of Entropy to Oligosaccharide Recognition at "Non-Primary" Binding Subsites.

Van Bueren, A.L.Boraston, A.B.

(2004) J Mol Biol 340: 869

  • DOI: https://doi.org/10.1016/j.jmb.2004.05.038
  • Primary Citation of Related Structures:  
    1UY1, 1UY2, 1UY3, 1UY4

  • PubMed Abstract: 

    The optimal ligands for many carbohydrate-binding proteins are often oligosaccharides comprising two, three, or more monosaccharide units. The binding affinity for these sugars is increased incrementally by contributions from binding subsites on the protein that accommodate the individual monosaccharide residues of the oligosaccharide. Here, we use CsCBM6-1, a xylan-specific type B carbohydrate-binding module (CBM) from Clostridium stercorarium falling into amino acid sequence family CBM6, as a model system to investigate the structural and thermodynamic contributions of binding subsites in this protein to carbohydrate recognition. The three-dimensional structures of uncomplexed CsCBM6-1 (at 1.8 A resolution) and bound to the oligosaccharides xylobiose, xylotriose, and xylotetraose (at 1.70 A, 1.89 A, and 1.69 A resolution, respectively) revealed the sequential occupation of four subsites within the binding site in the order of subsites 2, 3, 4 then 1. Overall, binding to all of the xylooligosaccharides tested was enthalpically favourable and entropically unfavourable, like most protein-carbohydrate interactions, with the primary subsites 2 and 3 providing the bulk of the free energy and enthalpy of binding. In contrast, the contributions to the changes in entropy of the non-primary subsites 1 and 4 to xylotriose and xylotetraose binding, respectively, were positive. This observation is remarkable, in that it shows that the 10-20-fold improvement in association constants for oligosaccharides longer than a disaccharide is facilitated by favourable entropic contributions from the non-primary binding subsites.

  • Organizational Affiliation

    Department of Biochemistry and Microbiology, University of Victoria, P.O. Box 3055 STN CSC, Victoria, BC, Canada V8W 3P6.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
ENDO-1,4-BETA-XYLANASE A145Thermoclostridium stercorariumMutation(s): 0 
Gene Names: xynA
Find proteins for Q8GJ44 (Thermoclostridium stercorarium)
Explore Q8GJ44 
Go to UniProtKB:  Q8GJ44
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ8GJ44
Sequence Annotations
  • Reference Sequence


Entity ID: 2
MoleculeChains Length2D Diagram Glycosylation3D Interactions
Glycosylation Resources
GlyTouCan:  G60650FG
GlyCosmos:  G60650FG
Experimental Data & Validation

Experimental Data

  • Resolution: 1.69 Å
  • R-Value Free: 0.177 
  • R-Value Work: 0.132 
  • R-Value Observed: 0.134 
  • Space Group: P 41 21 2
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 83.437α = 90
b = 83.437β = 90
c = 44.921γ = 90
Software Package:
Software NamePurpose
d*TREKdata reduction
d*TREKdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2004-06-18
    Type: Initial release
  • Version 1.1: 2011-05-07
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Version format compliance
  • Version 1.3: 2017-07-05
    Changes: Data collection
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Atomic model, Data collection, Derived calculations, Other, Structure summary