PDBsum entry: 1cen

Cellulose degradation

PDB id: 1cen

Contents

Protein chain

334 a.a. *

Ligands

BGC-BGC

Waters ×221

* Residue conservation analysis

PDB id:

1cen

Name:

Cellulose degradation

Title:

Cellulase (celc) mutant with glu 140 replaced by gln complexed with cellohexaose

Structure:

Cellulase celc. Chain: a. Synonym: 1,4-beta-d-glucan-glucanohydrolase, endo-1,4-beta- glucanasE C. Engineered: yes. Mutation: yes

Source:

Clostridium thermocellum. Organism_taxid: 1515. Strain: ncib 10682. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.30Å R-factor: 0.178 R-free: 0.246

Authors:

R.Dominguez,P.M.Alzari

Key ref:

R.Domínguez et al. (1996). The crystal structure of a family 5 endoglucanase mutant in complexed and uncomplexed forms reveals an induced fit activation mechanism. J Mol Biol, 257, 1042-1051. PubMed id: 8632467 DOI: 10.1006/jmbi.1996.0222

Date:

04-Dec-95 Release date: 03-Apr-96

Protein chain

P0C2S3  (GUNC_CLOTM) -  Endoglucanase C

Seq: 343 a.a.

Struc: 334 a.a.*

* PDB and UniProt seqs differ at 2 residue positions (black crosses)

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.

 Gene Ontology (GO) functional annotation 

• Biological process: metabolic process (4 terms)
• Biochemical function: catalytic activity (8 terms)

DOI no: 10.1006/jmbi.1996.0222

J Mol Biol 257:1042-1051 (1996)

PubMed id: 8632467

The crystal structure of a family 5 endoglucanase mutant in complexed and uncomplexed forms reveals an induced fit activation mechanism.

R.Domínguez, H.Souchon, M.Lascombe, P.M.Alzari.

ABSTRACT

The structures of the Glu140-->Gln mutant of the Clostridium thermocellum endoglucanase CelC in unliganded form (CelC(E140Q)) and in complex with cellohexaose (CelC(E140Q)-Gl(C6)) have been refined to crystallographic R-factors of 19.4% at 1.9 A and 17.8% at 2.3 A resolution, respectively. The structure of CelC(E140Q)-Gl(C6) complex shows two D-glucosyl residues bound to the non-reducing end of the substrate-binding cleft. Comparison of the unliganded and complexes structures reveals conformational changes due to substrate binding, including a significant reorientation of the loop 138-141 which carries the general acid/base catalyst Glu140 in wild-type CelC. Endoglucanase CelC, a family 5 glycohydrolase, exhibits a (beta/alpha)8-fold with an additional subdomain of 54 amino acids inserted between beta-strand 6 and alpha-helix 6. Seven amino acid residues (Arg46, His90, Asn139, Glu140, His198, Tyr200, and Glu280) located close to the catalytic reaction center are strictly conserved in family 5 cellulases. Only three of these residues (His90, Gln140 and Glu280) make direct contacts with the substrate, but all participate in a network of hydrogen bonds which contribute to the stability of the active site architecture and may influence the protonation state of the two catalytic residues. Residue Trp313, which interacts with the nucleophile Glu280 and is within hydrogen bonding distance of the substrate, is involved in a non-proline cis-peptide bond. An aromatic residue occurs at an equivalent position in many other (beta/alpha)8-barrel glycosidases; the presence of a cis-peptide bond at this position in the structures of family 1 beta-glucosidases, family 2 beta-galactosidases, family 5 cellulases, family 17 beta-glucanases, and family 18 chitinases provides further evidence of an evolutionary relationship between glycosyl hydrolases with a (beta/alpha)8- architecture.

Selected figure(s)

Figure 2.
Figure 2. Stereo view of the active site of the CelCE140Q--Glc6 complex illustrating the hydrogen-bonding network (broken lines) involving Trp313 and seven amino acid residues conserved in family 5 cellulases. The corresponding distances are listed in Table 1. The drawing was generated with MOLSCRIPT (Kraulis, 1991).

Figure 6.
Figure 6. The cis-peptide bond between Trp313 and Asn314 of CelC is stabilized by an internal water molecule which is involved in a tetrahedral arrangement of hydrogen bonds with protein atoms.

The above figures are reprinted by permission from Elsevier: J Mol Biol (1996, 257, 1042-1051) copyright 1996.

Figures were selected by an automated process.