PDBsum entry 2bvd

Hydrolase

PDB id: 2bvd

Contents

Protein chain

276 a.a. *

Ligands

ISX

Waters ×374

* Residue conservation analysis

PDB id:

2bvd

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: egh, endo-1,4-beta-glucanase, cellulase h, lich26a. Engineered: yes

Source:

Clostridium thermocellum. Organism_taxid: 1515. Strain: f1/ys. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

1.60Å R-factor: 0.156 R-free: 0.186

Authors:

E.J.Taylor,A.Goyal,C.I.P.D.Guerreiro,J.A.M.Prates,V.A.Money,N.Ferry, 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

Date:

27-Jun-05 Release date: 30-Jun-05

Protein chain

P16218  (GUNH_CLOTH) -  Endoglucanase H from Acetivibrio thermocellus (strain ATCC 27405 / DSM 1237 / JCM 9322 / NBRC 103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372)

Seq: 900 a.a.

Struc: 276 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.3.2.1.4 - cellulase.
• Reaction: Endohydrolysis of 1,4-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans.

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.

ABSTRACT

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.