Crystal structure of PbGH5A, a glycoside hydrolase family 5 member from Prevotella bryantii B14, in complex with the xyloglucan heptasaccharide XXXG

Experimental Data Snapshot

  • Resolution: 1.86 Å
  • R-Value Free: 0.168 
  • R-Value Work: 0.139 
  • R-Value Observed: 0.139 

wwPDB Validation   3D Report Full Report

This is version 2.1 of the entry. See complete history


Structure-Function Analysis of a Mixed-linkage beta-Glucanase/Xyloglucanase from the Key Ruminal Bacteroidetes Prevotella bryantii B14.

McGregor, N.Morar, M.Fenger, T.H.Stogios, P.Lenfant, N.Yin, V.Xu, X.Evdokimova, E.Cui, H.Henrissat, B.Savchenko, A.Brumer, H.

(2016) J Biol Chem 291: 1175-1197

  • DOI: https://doi.org/10.1074/jbc.M115.691659
  • Primary Citation of Related Structures:  
    3VDH, 5D9M, 5D9N, 5D9O, 5D9P

  • PubMed Abstract: 

    The recent classification of glycoside hydrolase family 5 (GH5) members into subfamilies enhances the prediction of substrate specificity by phylogenetic analysis. However, the small number of well characterized members is a current limitation to understanding the molecular basis of the diverse specificity observed across individual GH5 subfamilies. GH5 subfamily 4 (GH5_4) is one of the largest, with known activities comprising (carboxymethyl)cellulases, mixed-linkage endo-glucanases, and endo-xyloglucanases. Through detailed structure-function analysis, we have revisited the characterization of a classic GH5_4 carboxymethylcellulase, PbGH5A (also known as Orf4, carboxymethylcellulase, and Cel5A), from the symbiotic rumen Bacteroidetes Prevotella bryantii B14. We demonstrate that carboxymethylcellulose and phosphoric acid-swollen cellulose are in fact relatively poor substrates for PbGH5A, which instead exhibits clear primary specificity for the plant storage and cell wall polysaccharide, mixed-linkage β-glucan. Significant activity toward the plant cell wall polysaccharide xyloglucan was also observed. Determination of PbGH5A crystal structures in the apo-form and in complex with (xylo)glucan oligosaccharides and an active-site affinity label, together with detailed kinetic analysis using a variety of well defined oligosaccharide substrates, revealed the structural determinants of polysaccharide substrate specificity. In particular, this analysis highlighted the PbGH5A active-site motifs that engender predominant mixed-linkage endo-glucanase activity vis à vis predominant endo-xyloglucanases in GH5_4. However the detailed phylogenetic analysis of GH5_4 members did not delineate particular clades of enzymes sharing these sequence motifs; the phylogeny was instead dominated by bacterial taxonomy. Nonetheless, our results provide key enzyme functional and structural reference data for future bioinformatics analyses of (meta)genomes to elucidate the biology of complex gut ecosystems.

  • Organizational Affiliation

    From the Michael Smith Laboratories and Department of Chemistry, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
353Segatella bryantiiMutation(s): 0 
Find proteins for O06842 (Segatella bryantii)
Explore O06842 
Go to UniProtKB:  O06842
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupO06842
Sequence Annotations
  • Reference Sequence


Entity ID: 2
MoleculeChains Length2D Diagram Glycosylation3D Interactions
C, D
Glycosylation Resources
GlyTouCan:  G24181CY
GlyCosmos:  G24181CY
Experimental Data & Validation

Experimental Data

  • Resolution: 1.86 Å
  • R-Value Free: 0.168 
  • R-Value Work: 0.139 
  • R-Value Observed: 0.139 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 75.56α = 90
b = 84.116β = 90
c = 138.63γ = 90
Software Package:
Software NamePurpose
HKL-3000data reduction
HKL-3000data scaling
Cootmodel building

Structure Validation

View Full Validation Report

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2015-11-04
    Type: Initial release
  • Version 1.1: 2015-11-11
    Changes: Database references
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Atomic model, Data collection, Database references, Derived calculations, Structure summary
  • Version 2.1: 2023-09-27
    Changes: Data collection, Database references, Derived calculations, Refinement description, Structure summary