Crystal structure of a fungal chimeric cellobiohydrolase Cel6A

Experimental Data Snapshot

  • Resolution: 1.22 Å
  • R-Value Free: 0.158 
  • R-Value Work: 0.143 
  • R-Value Observed: 0.143 

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This is version 1.2 of the entry. See complete history


Engineered thermostable fungal Cel6A and Cel7A cellobiohydrolases hydrolyze cellulose efficiently at elevated temperatures.

Wu, I.Arnold, F.H.

(2013) Biotechnol Bioeng 110: 1874-1883

  • DOI: https://doi.org/10.1002/bit.24864
  • Primary Citation of Related Structures:  
    4I5R, 4I5U

  • PubMed Abstract: 

    Thermostability is an important feature in industrial enzymes: it increases biocatalyst lifetime and enables reactions at higher temperatures, where faster rates and other advantages ultimately reduce the cost of biocatalysis. Here we report the thermostabilization of a chimeric fungal family 6 cellobiohydrolase (HJPlus) by directed evolution using random mutagenesis and recombination of beneficial mutations. Thermostable variant 3C6P has a half-life of 280 min at 75°C and a T(50) of 80.1°C, a ~15°C increase over the thermostable Cel6A from Humicola insolens (HiCel6A) and a ~20°C increase over that from Hypocrea jecorina (HjCel6A). Most of the mutations also stabilize the less-stable HjCel6A, the wild-type Cel6A closest in sequence to 3C6P. During a 60-h Avicel hydrolysis, 3C6P released 2.4 times more cellobiose equivalents at its optimum temperature (T(opt)) of 75°C than HiCel6A at its T(opt) of 60°C. The total cellobiose equivalents released by HiCel6A at 60°C after 60 h is equivalent to the total released by 3C6P at 75°C after ~6 h, a 10-fold reduction in hydrolysis time. A binary mixture of thermostable Cel6A and Cel7A hydrolyzes Avicel synergistically and released 1.8 times more cellobiose equivalents than the wild-type mixture, both mixtures assessed at their respective T(opt). Crystal structures of HJPlus and 3C6P, determined at 1.5 and 1.2 Å resolution, indicate that the stabilization comes from improved hydrophobic interactions and restricted loop conformations by introduced proline residues.

  • Organizational Affiliation

    Division of Chemistry and Chemical Engineering, California Institute of Technology 210-41, Pasadena, CA 91125, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Chimeric cel6A364Humicola insolensThermochaetoides thermophilaTrichoderma reeseiMutation(s): 6 
Gene Names: avi2cel6Acbh2
EC: (PDB Primary Data), 3.2.1 (UniProt)
Find proteins for P07987 (Hypocrea jecorina)
Explore P07987 
Go to UniProtKB:  P07987
Find proteins for Q9C1S9 (Humicola insolens)
Explore Q9C1S9 
Go to UniProtKB:  Q9C1S9
Find proteins for Q5G2D4 (Thermochaetoides thermophila)
Explore Q5G2D4 
Go to UniProtKB:  Q5G2D4
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupsP07987Q5G2D4Q9C1S9
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 4 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on PG4

Download Ideal Coordinates CCD File 
C8 H18 O5
Query on PGE

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O [auth A],
P [auth A]
C6 H14 O4
Query on EDO

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D [auth A]
E [auth A]
F [auth A]
G [auth A]
H [auth A]
D [auth A],
E [auth A],
F [auth A],
G [auth A],
H [auth A],
I [auth A],
J [auth A],
K [auth A],
L [auth A],
M [auth A]
C2 H6 O2
Query on ACT

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B [auth A],
C [auth A]
C2 H3 O2
Experimental Data & Validation

Experimental Data

  • Resolution: 1.22 Å
  • R-Value Free: 0.158 
  • R-Value Work: 0.143 
  • R-Value Observed: 0.143 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 158.599α = 90
b = 45.414β = 95.47
c = 58.194γ = 90
Software Package:
Software NamePurpose
SCALAdata scaling
PDB_EXTRACTdata extraction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2013-04-03
    Type: Initial release
  • Version 1.1: 2013-06-12
    Changes: Database references
  • Version 1.2: 2017-08-09
    Changes: Refinement description, Source and taxonomy