PDBsum entry 2rfw

Hydrolase

PDB id: 2rfw

Contents

Protein chains

430 a.a. *

Waters ×689

* Residue conservation analysis

PDB id:

2rfw

Name:

Hydrolase

Title:

Crystal structure of cellobiohydrolase from melanocarpus albomyces

Structure:

Cellulose 1,4-beta-cellobiosidase. Chain: a, b, c, d. Engineered: yes. Mutation: yes

Source:

Melanocarpus albomyces. Organism_taxid: 204285. Expressed in: trichoderma reesei. Expression_system_taxid: 51453

Resolution:

1.60Å R-factor: 0.199 R-free: 0.243

Authors:

T.Parkkinen,A.Koivula,J.Vehmaanper,J.Rouvinen

Key ref:

T.Parkkinen et al. (2008). Crystal structures of Melanocarpus albomyces cellobiohydrolase Cel7B in complex with cello-oligomers show high flexibility in the substrate binding. Protein Sci, 17, 1383-1394. PubMed id: 18499583 DOI: 10.1110/ps.034488.108

Date:

02-Oct-07 Release date: 16-Sep-08

Protein chains

Q8J0K6  (Q8J0K6_MELAO) -  Glucanase from Melanocarpus albomyces

Seq: 452 a.a.

Struc: 430 a.a.*

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

Enzyme reactions

• Enzyme class 1: E.C.3.2.1.- - ?????
• Enzyme class 2: E.C.3.2.1.91 - cellulose 1,4-beta-cellobiosidase (non-reducing end).
• Reaction: Hydrolysis of 1,4-beta-D-glucosidic linkages in cellulose and cellotetraose, releasing cellobiose from the non-reducing ends of the chains.

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

DOI no: 10.1110/ps.034488.108

Protein Sci 17:1383-1394 (2008)

PubMed id: 18499583

Crystal structures of Melanocarpus albomyces cellobiohydrolase Cel7B in complex with cello-oligomers show high flexibility in the substrate binding.

T.Parkkinen, A.Koivula, J.Vehmaanperä, J.Rouvinen.

ABSTRACT

Cellobiohydrolase from Melanocarpus albomyces (Cel7B) is a thermostable, single-module, cellulose-degrading enzyme. It has relatively low catalytic activity under normal temperatures, which allows structural studies of the binding of unmodified substrates to the native enzyme. In this study, we have determined the crystal structure of native Ma Cel7B free and in complex with three different cello-oligomers: cellobiose (Glc(2)), cellotriose (Glc(3)), and cellotetraose (Glc(4)), at high resolution (1.6-2.1 A). In each case, four molecules were found in the asymmetric unit, which provided 12 different complex structures. The overall fold of the enzyme is characteristic of a glycoside hydrolase family 7 cellobiohydrolase, where the loops extending from the core beta-sandwich structure form a long tunnel composed of multiple subsites for the binding of the glycosyl units of a cellulose chain. The catalytic residues at the reducing end of the tunnel are conserved, and the mechanism is expected to be retaining similarly to the other family 7 members. The oligosaccharides in different complex structures occupied different subsite sets, which partly overlapped and ranged from -5 to +2. In four cellotriose and one cellotetraose complex structures, the cello-oligosaccharide also spanned over the cleavage site (-1/+1). There were surprisingly large variations in the amino acid side chain conformations and in the positions of glycosyl units in the different cello-oligomer complexes, particularly at subsites near the catalytic site. However, in each complex structure, all glycosyl residues were in the chair (4C(1)) conformation. Implications in relation to the complex structures with respect to the reaction mechanism are discussed.

Selected figure(s)

Figure 2.
Figure 2. (A–C) Active site superposition of the four molecules in the asymmetric unit in stereo. (A) Cellobiose, (B) cellotriose, and (C) cellotetraose soaked structures. Observed cello-oligomers are in green and red. The side chains of amino acid residues in the cellulose-binding site are in gray. (D) Superposition of all 12 active sites with cellulose chain modeled in Tr Cel7A structure (blue) in stereoview.

Figure 3.
Figure 3. Protein–carbohydrate-hydrogen-bonding interactions in the active site tunnel of Ma Cel7B. The interactions are collected from all 12 complex structures. Hydrogen bonds are indicated with broken lines.

The above figures are reprinted by permission from the Protein Society: Protein Sci (2008, 17, 1383-1394) copyright 2008.

Figures were selected by an automated process.