Chitosan Product complex of Amycolatopsis orientalis exo-chitosanase CsxA

Experimental Data Snapshot

  • Resolution: 1.85 Å
  • R-Value Free: 0.220 
  • R-Value Work: 0.173 
  • R-Value Observed: 0.175 

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The Structural Basis of Substrate Recognition in an Exo-Beta-D-Glucosaminidase Involved in Chitosan Hydrolysis.

Lammerts Van Bueren, A.Ghinet, M.G.Gregg, K.Fleury, A.Brzezinski, R.Boraston, A.B.

(2009) J Mol Biol 385: 131

  • DOI: https://doi.org/10.1016/j.jmb.2008.10.031
  • Primary Citation of Related Structures:  
    2VZO, 2VZS, 2VZT, 2VZU, 2VZV

  • PubMed Abstract: 

    Family 2 of the glycoside hydrolase classification is one of the largest families. Structurally characterized members of this family include enzymes with beta-galactosidase activity (Escherichia coli LacZ), beta-glucuronidase activity (Homo sapiens GusB), and beta-mannosidase activity (Bacteroides thetaiotaomicron BtMan2A). Here, we describe the structure of a family 2 glycoside hydrolase, CsxA, from Amycolatopsis orientalis that has exo-beta-D-glucosaminidase (exo-chitosanase) activity. Analysis of a product complex (1.85 A resolution) reveals a unique negatively charged pocket that specifically accommodates the nitrogen of nonreducing end glucosamine residues, allowing this enzyme to discriminate between glucose and glucosamine. This also provides structural evidence for the role of E541 as the catalytic nucleophile and D469 as the catalytic acid/base. The structures of an E541A mutant in complex with a natural beta-1,4-D-glucosamine tetrasaccharide substrate and both E541A and D469A mutants in complex with a pNP-beta-D-glucosaminide synthetic substrate provide insight into interactions in the +1 subsite of this enzyme. Overall, a comparison with the active sites of other GH2 enzymes highlights the unique architecture of the CsxA active site, which imparts specificity for its cationic substrate.

  • Organizational Affiliation

    Biochemistry and Microbiology, University of Victoria, BC, Canada.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B
1,032Amycolatopsis orientalisMutation(s): 0 
Find proteins for Q56F26 (Amycolatopsis orientalis)
Explore Q56F26 
Go to UniProtKB:  Q56F26
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ56F26
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 3 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on GCS

Download Ideal Coordinates CCD File 
F [auth A],
L [auth B]
C6 H13 N O5
Query on CD

Download Ideal Coordinates CCD File 
C [auth A]
D [auth A]
E [auth A]
H [auth B]
I [auth B]
C [auth A],
D [auth A],
E [auth A],
H [auth B],
I [auth B],
J [auth B]
Query on GOL

Download Ideal Coordinates CCD File 
G [auth A],
K [auth B],
M [auth B]
C3 H8 O3
Experimental Data & Validation

Experimental Data

  • Resolution: 1.85 Å
  • R-Value Free: 0.220 
  • R-Value Work: 0.173 
  • R-Value Observed: 0.175 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 86.544α = 90
b = 121.81β = 90.42
c = 91.843γ = 90
Software Package:
Software NamePurpose

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2008-10-14
    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 1.4: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Data collection, Derived calculations, Other, Structure summary