PDBsum entry 2eex

Hydrolase

PDB id: 2eex

Contents

Protein chain

509 a.a. *

Ligands

BGC-BGC-BGC-BGC-BGC

GOL ×2

Metals

_CA

_ZN

_CL

Waters ×459

* Residue conservation analysis

PDB id:

2eex

Name:

Hydrolase

Title:

Crystal structure of cel44a, gh family 44 endoglucanase from clostridium thermocellum

Structure:

Endoglucanase. Chain: a. Fragment: residues 1-519. Synonym: glycoside hydrolase. Engineered: yes. Mutation: yes

Source:

Clostridium thermocellum. Organism_taxid: 1515. Strain: f1. Gene: cel44a. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.00Å R-factor: 0.165 R-free: 0.201

Authors:

Y.Kitago,S.Karita,N.Watanabe,K.Sakka,I.Tanaka

Key ref:

Y.Kitago et al. (2007). Crystal structure of Cel44A, a glycoside hydrolase family 44 endoglucanase from Clostridium thermocellum. J Biol Chem, 282, 35703-35711. PubMed id: 17905739 DOI: 10.1074/jbc.M706835200

Date:

19-Feb-07 Release date: 18-Sep-07

Protein chain

A3DD30  (A3DD30_CLOTH) -  Glycoside hydrolase family 9 from Acetivibrio thermocellus (strain ATCC 27405 / DSM 1237 / JCM 9322 / NBRC 103400 / NCIMB 10682 / NRRL B-4536 / VPI 7372)

Seq: 1601 a.a.

Struc: 509 a.a.*

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

Enzyme reactions

• Enzyme class 2: E.C.3.2.1.151 - xyloglucan-specific endo-beta-1,4-glucanase.
• Reaction: xyloglucan + H2O = xyloglucan oligosaccharides
• Enzyme class 3: E.C.3.2.1.4 - cellulase.
• Reaction: Endohydrolysis of 1,4-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans.

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: 10.1074/jbc.M706835200

J Biol Chem 282:35703-35711 (2007)

PubMed id: 17905739

Crystal structure of Cel44A, a glycoside hydrolase family 44 endoglucanase from Clostridium thermocellum.

Y.Kitago, S.Karita, N.Watanabe, M.Kamiya, T.Aizawa, K.Sakka, I.Tanaka.

ABSTRACT

The crystal structure of Cel44A, which is one of the enzymatic components of the cellulosome of Clostridium thermocellum, was solved at a resolution of 0.96 A. This enzyme belongs to glycoside hydrolase family (GH family) 44. The structure reveals that Cel44A consists of a TIM-like barrel domain and a beta-sandwich domain. The wild-type and the E186Q mutant structures complexed with substrates suggest that two glutamic acid residues, Glu(186) and Glu(359), are the active residues of the enzyme. Biochemical experiments were performed to confirm this idea. The structural features indicate that GH family 44 belongs to clan GH-A and that the reaction catalyzed by Cel44A is retaining type hydrolysis. The stereochemical course of hydrolysis was confirmed by a (1)H NMR experiment using the reduced cellooligosaccharide as a substrate.

Selected figure(s)

Figure 2.
a, the reaction product recognition of the minus subsite observed with F[o] – F[c] electron density map contoured 2.0σ in the wild-type crystal structure complexed with cellohexaose. b, the substrate-recognizing residues and four hydrogen bonds between the reaction product and the wild-type Cel44A molecule in the crystal structure. c, close up stereoview of the reducing end pyranose ring. The F[o] – F[c] electron density map is shown as a gray surface contoured 2.0σ. The map is shown in the region of 3.0 Å distance around the substrate in a and c.

Figure 5.
The F[o] – F[c] electron density map contoured at 2.2σ around subsite –1 in the E186Q mutant complexed with a high concentration of cellohexaose. The map is shown in the region of 3.0 Å distance around the substrate. Shown is the model of the E186Q mutant structure complexed with a high concentration of cellohexaose.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2007, 282, 35703-35711) copyright 2007.

Figures were selected by an automated process.