PDBsum entry 1qk2

Hydrolase

PDB id: 1qk2

Contents

Protein chains

363 a.a. *

Ligands

MGL-SGC-GLC-GLC ×2

NAG ×4

MAN ×14

Waters ×545

* Residue conservation analysis

PDB id:

1qk2

Name:

Hydrolase

Title:

Wild type cel6a with a non-hydrolysable cellotetraose

Structure:

Cellobiohydrolase cel6a (formerly called cbh ii). Chain: a, b. Fragment: catalytic domain, residues 85-447. Synonym: cel6a. Engineered: yes

Source:

Trichoderma reesei. Organism_taxid: 51453. Gene: cbh2. Expressed in: trichoderma reesei. Expression_system_taxid: 51453

Resolution:

2.00Å R-factor: 0.189 R-free: 0.222

Authors:

J.-Y.Zou,T.A.Jones

Key ref:

J.Zou et al. (1999). Crystallographic evidence for substrate ring distortion and protein conformational changes during catalysis in cellobiohydrolase Ce16A from trichoderma reesei. Structure, 7, 1035-1045. PubMed id: 10508787 DOI: 10.1016/S0969-2126(99)80171-3

Date:

09-Jul-99 Release date: 18-Sep-99

Protein chains

P07987  (GUX2_HYPJE) -  Exoglucanase 2 from Hypocrea jecorina

Seq: 471 a.a.

Struc: 363 a.a.

Enzyme reactions

• Enzyme class: 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.

DOI no: 10.1016/S0969-2126(99)80171-3

Structure 7:1035-1045 (1999)

PubMed id: 10508787

Crystallographic evidence for substrate ring distortion and protein conformational changes during catalysis in cellobiohydrolase Ce16A from trichoderma reesei.

J.Zou, G.J.Kleywegt, J.Ståhlberg, H.Driguez, W.Nerinckx, M.Claeyssens, A.Koivula, T.T.Teeri, T.A.Jones.

ABSTRACT

BACKGROUND: Cel6A is one of the two cellobiohydrolases produced by Trichoderma reesei. The catalytic core has a structure that is a variation of the classic TIM barrel. The active site is located inside a tunnel, the roof of which is formed mainly by a pair of loops. RESULTS: We describe three new ligand complexes. One is the structure of the wild-type enzyme in complex with a nonhydrolysable cello-oligosaccharide, methyl 4-S-beta-cellobiosyl-4-thio-beta-cellobioside (Glc)(2)-S-(Glc)(2), which differs from a cellotetraose in the nature of the central glycosidic linkage where a sulphur atom replaces an oxygen atom. The second structure is a mutant, Y169F, in complex with the same ligand, and the third is the wild-type enzyme in complex with m-iodobenzyl beta-D-glucopyranosyl-beta(1,4)-D-xylopyranoside (IBXG). CONCLUSIONS: The (Glc)(2)-S-(Glc)(2) ligand binds in the -2 to +2 sites in both the wild-type and mutant enzymes. The glucosyl unit in the -1 site is distorted from the usual chair conformation in both structures. The IBXG ligand binds in the -2 to +1 sites, with the xylosyl unit in the -1 site where it adopts the energetically favourable chair conformation. The -1 site glucosyl of the (Glc)(2)-S-(Glc)(2) ligand is unable to take on this conformation because of steric clashes with the protein. The crystallographic results show that one of the tunnel-forming loops in Cel6A is sensitive to modifications at the active site, and is able to take on a number of different conformations. One of the conformational changes disrupts a set of interactions at the active site that we propose is an integral part of the reaction mechanism.

Selected figure(s)

Figure 2.
Figure 2. Close-up view of the -2 to +2 binding sites in the WT-(Glc)[2]-S-(Glc)[2] structure. Only residues interacting with the ligand are included, except for Arg353 (to illustrate the interaction of Asp401-Arg353). Colours in the cartoon are ramped from red at the N terminus to blue at the C terminus. Sidechain atoms are coloured golden for carbon, blue for nitrogen and red for oxygen. In the ligand, carbons are golden, oxygens are magenta and the linking sulphur is green. Water molecules that make hydrogen bonds with ligand or protein atoms are drawn as small yellow spheres.

The above figure is reprinted by permission from Cell Press: Structure (1999, 7, 1035-1045) copyright 1999.

Figure was selected by the author.