1RQ5

Structural Basis for the Exocellulase Activity of the Cellobiohydrolase CbhA from C. thermocellum


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.4 Å
  • R-Value Free: 0.270 
  • R-Value Work: 0.210 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

Structural basis for the exocellulase activity of the cellobiohydrolase CbhA from Clostridium thermocellum

Schubot, F.D.Kataeva, I.A.Chang, J.Shah, A.K.Ljungdahl, L.G.Rose, J.P.Wang, B.C.

(2004) Biochemistry 43: 1163-1170

  • DOI: 10.1021/bi030202i
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • Numerous bacterial and fungal organisms have evolved elaborate sets of modular glycoside hydrolases and similar enzymes aimed at the degradation of polymeric carbohydrates. Presently, on the basis of sequence similarity catalytic modules of these enz ...

    Numerous bacterial and fungal organisms have evolved elaborate sets of modular glycoside hydrolases and similar enzymes aimed at the degradation of polymeric carbohydrates. Presently, on the basis of sequence similarity catalytic modules of these enzymes have been classified into 90 families. Representatives of a particular family display similar fold and catalytic mechanisms. However, within families distinctions occur with regard to enzymatic properties and type of activity against carbohydrate chains. Cellobiohydrolase CbhA from Clostridium thermocellum is a large seven-modular enzyme with a catalytic module belonging to family 9. In contrast to other representatives of that family possessing only endo- and, in few cases, endo/exo-cellulase activities, CbhA is exclusively an exocellulase. The crystal structures of the combination of the immunoglobulin-like module and the catalytic module of CbhA (Ig-GH9_CbhA) and that of an inactive mutant Ig-GH9_CbhA(E795Q) in complex with cellotetraose (CTT) are reported here. The detailed analysis of these structures reveals that, while key catalytic residues and overall fold are conserved in this enzyme and those of other family 9 glycoside hydrolases, the active site of GH9_CbhA is blocked off after the -2 subsite. This feature which is created by an extension and altered conformation of a single loop region explains the inability of the active site of CbhA to accommodate a long cellulose chain and to cut it internally. This altered loop region is responsible for the exocellulolytic activity of the enzyme.


    Organizational Affiliation

    Department of Biochemistry & Molecular Biology, The University of Georgia, Athens, Georgia 30602, USA.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Cellobiohydrolase
A
610Clostridium thermocellumMutation(s): 1 
Gene Names: cbhA
EC: 3.2.1.-
Find proteins for Q59325 (Clostridium thermocellum)
Go to UniProtKB:  Q59325
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CTT
Query on CTT

Download SDF File 
Download CCD File 
A
beta-D-glucopyranosyl-(1->4)-beta-D-glucopyranosyl-(1->4)-beta-D-glucopyranosyl-(1->4)-beta-D-glucopyranose
CELLOTETRAOSE
C24 H42 O21
LUEWUZLMQUOBSB-HGDSAIHNSA-N
 Ligand Interaction
CA
Query on CA

Download SDF File 
Download CCD File 
A
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.4 Å
  • R-Value Free: 0.270 
  • R-Value Work: 0.210 
  • Space Group: P 61
Unit Cell:
Length (Å)Angle (°)
a = 108.600α = 90.00
b = 108.600β = 90.00
c = 119.180γ = 120.00
Software Package:
Software NamePurpose
PROTEUM PLUSdata reduction
CNSphasing
PROTEUM PLUSdata scaling
CNSrefinement
PROTEUM PLUSdata collection

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2004-03-30
    Type: Initial release
  • Version 1.1: 2008-04-29
    Type: Version format compliance
  • Version 1.2: 2011-07-13
    Type: Version format compliance