PDBsum entry 2bv9

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protein links
Hydrolase PDB id
Protein chain
284 a.a. *
Waters ×465
* Residue conservation analysis
PDB id:
Name: Hydrolase
Title: How family 26 glycoside hydrolases orchestrate catalysis on different polysaccharides. Structure and activity of a clostridium thermocellum lichenase, ctlic26a
Structure: Endoglucanase h. Chain: a. Fragment: catalytic domain, residues 26-304. Synonym: cellulose binding protein a, egh, endo-1,4-beta-gl cellulase h, lich26a. Engineered: yes
Source: Clostridium thermocellum. Organism_taxid: 1515. Strain: f1/ys. Expressed in: escherichia coli. Expression_system_taxid: 469008.
1.50Å     R-factor:   0.132     R-free:   0.157
Authors: E.J.Taylor,A.Goyal,C.I.P.D.Guerreiro,J.A.M.Prates,V.A.Money, C.Morland,A.Planas,J.A.Macdonald,R.V.Stick,H.J.Gilbert, C.M.G.A.Fontes,G.J.Davies
Key ref:
E.J.Taylor et al. (2005). How family 26 glycoside hydrolases orchestrate catalysis on different polysaccharides: structure and activity of a Clostridium thermocellum lichenase, CtLic26A. J Biol Chem, 280, 32761-32767. PubMed id: 15987675 DOI: 10.1074/jbc.M506580200
23-Jun-05     Release date:   30-Jun-05    
Go to PROCHECK summary

Protein chain
Pfam   ArchSchema ?
P16218  (GUNH_CLOTH) -  Endoglucanase H
900 a.a.
284 a.a.*
Key:    PfamA domain  Secondary structure  CATH domain
* PDB and UniProt seqs differ at 8 residue positions (black crosses)

 Enzyme reactions 
   Enzyme class: E.C.  - Cellulase.
[IntEnz]   [ExPASy]   [KEGG]   [BRENDA]
      Reaction: Endohydrolysis of 1,4-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans.
 Gene Ontology (GO) functional annotation 
  GO annot!
  Biological process     carbohydrate metabolic process   2 terms 
  Biochemical function     cellulase activity     2 terms  


DOI no: 10.1074/jbc.M506580200 J Biol Chem 280:32761-32767 (2005)
PubMed id: 15987675  
How family 26 glycoside hydrolases orchestrate catalysis on different polysaccharides: structure and activity of a Clostridium thermocellum lichenase, CtLic26A.
E.J.Taylor, A.Goyal, C.I.Guerreiro, J.A.Prates, V.A.Money, N.Ferry, C.Morland, A.Planas, J.A.Macdonald, R.V.Stick, H.J.Gilbert, C.M.Fontes, G.J.Davies.
One of the most intriguing features of the 90 glycoside hydrolase families (GHs) is the range of specificities displayed by different members of the same family, whereas the catalytic apparatus and mechanism are often invariant. Family GH26 predominantly comprises beta-1,4 mannanases; however, a bifunctional Clostridium thermocellum GH26 member (hereafter CtLic26A) displays a markedly different specificity. We show that CtLic26A is a lichenase, specific for mixed (Glcbeta1,4Glcbeta1,4Glcbeta1,3)n oligo- and polysaccharides, and displays no activity on manno-configured substrates or beta-1,4-linked homopolymers of glucose or xylose. The three-dimensional structure of the native form of CtLic26A has been solved at 1.50-A resolution, revealing a characteristic (beta/alpha)8 barrel with Glu-109 and Glu-222 acting as the catalytic acid/base and nucleophile in a double-displacement mechanism. The complex with the competitive inhibitor, Glc-beta-1,3-isofagomine (Ki 1 microm), at 1.60 A sheds light on substrate recognition in the -2 and -1 subsites and illuminates why the enzyme is specific for lichenan-based substrates. Hydrolysis of beta-mannosides by GH26 members is thought to proceed through transition states in the B2,5 (boat) conformation in which structural distinction of glucosides versus mannosides reflects not the configuration at C2 but the recognition of the pseudoaxial O3 of the B2,5 conformation. We suggest a different conformational itinerary for the GH26 enzymes active on gluco-configured substrates.
  Selected figure(s)  
Figure 1.
FIGURE 1. Schematic of the molecular architecture of CtLic26A-Cel5E. The modules encoded by the defined recombinant plasmids are indicated with the gray and black boxes representing the signal peptide and linker sequences, respectively.
Figure 4.
FIGURE 4. Schematic diagram of the interactions of the C. thermocellum CtLic26A with Glc-IsoF.
  The above figures are reprinted by permission from the ASBMB: J Biol Chem (2005, 280, 32761-32767) copyright 2005.  
  Figures were selected by an automated process.  

Literature references that cite this PDB file's key reference

  PubMed id Reference
18799462 A.Cartmell, E.Topakas, V.M.Ducros, M.D.Suits, G.J.Davies, and H.J.Gilbert (2008).
The Cellvibrio japonicus mannanase CjMan26C displays a unique exo-mode of action that is conferred by subtle changes to the distal region of the active site.
  J Biol Chem, 283, 34403-34413.
PDB codes: 2vx4 2vx5 2vx6 2vx7
18292875 V.A.Money, A.Cartmell, C.I.Guerreiro, V.M.Ducros, C.M.Fontes, H.J.Gilbert, and G.J.Davies (2008).
Probing the beta-1,3:1,4 glucanase, CtLic26A, with a thio-oligosaccharide and enzyme variants.
  Org Biomol Chem, 6, 851-853.
PDB code: 2vi0
17327666 M.Carson, D.H.Johnson, H.McDonald, C.Brouillette, and L.J.Delucas (2007).
His-tag impact on structure.
  Acta Crystallogr D Biol Crystallogr, 63, 295-301.  
16823793 V.A.Money, N.L.Smith, A.Scaffidi, R.V.Stick, H.J.Gilbert, and G.J.Davies (2006).
Substrate distortion by a lichenase highlights the different conformational itineraries harnessed by related glycoside hydrolases.
  Angew Chem Int Ed Engl, 45, 5136-5140.
PDB codes: 2cip 2cit
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