PDBsum entry 1heh

Hydrolase(xylan degradation)

PDB id: 1heh

Contents

Protein chain

88 a.a. *

* Residue conservation analysis

PDB id:

1heh

Name:

Hydrolase(xylan degradation)

Title:

C-terminal xylan binding domain from cellulomonas fimi xylanase 11a

Structure:

Endo-1,4-beta-xylanase d. Chain: c. Fragment: xylan binding domain 2. Synonym: xylanase d, cbm2b-2, xbd2. Engineered: yes

Source:

Cellulomonas fimi. Organism_taxid: 1708. Strain: jm83. Expressed in: escherichia coli. Expression_system_taxid: 469008.

NMR struc:

1 models

Authors:

P.J.Simpson,X.Hefang,D.N.Bolam,P.White,S.M.Hancock,H.J.Gilbert, M.P.Williamson

Key ref:

D.N.Bolam et al. (2001). Evidence for synergy between family 2b carbohydrate binding modules in Cellulomonas fimi xylanase 11A. Biochemistry, 40, 2468-2477. PubMed id: 11327868 DOI: 10.1021/bi002564l

Date:

22-Nov-00 Release date: 10-May-01

Protein chain

P54865  (XYND_CELFI) -  Bifunctional xylanase/deacetylase from Cellulomonas fimi

Seq: 644 a.a.

Struc: 88 a.a.

Enzyme reactions

• Enzyme class 2: E.C.3.2.1.8 - endo-1,4-beta-xylanase.
• Reaction: Endohydrolysis of 1,4-beta-D-xylosidic linkages in xylans.
• Enzyme class 3: E.C.3.5.1.- - ?????

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: 10.1021/bi002564l

Biochemistry 40:2468-2477 (2001)

PubMed id: 11327868

Evidence for synergy between family 2b carbohydrate binding modules in Cellulomonas fimi xylanase 11A.

D.N.Bolam, H.Xie, P.White, P.J.Simpson, S.M.Hancock, M.P.Williamson, H.J.Gilbert.

ABSTRACT

Glycoside hydrolases often contain multiple copies of noncatalytic carbohydrate binding modules (CBMs) from the same or different families. Currently, the functional importance of this complex molecular architecture is unclear. To investigate the role of multiple CBMs in plant cell wall hydrolases, we have determined the polysaccharide binding properties of wild type and various derivatives of Cellulomonas fimi xylanase 11A (Cf Xyn11A). This protein, which binds to both cellulose and xylan, contains two family 2b CBMs that exhibit 70% sequence identity, one internal (CBM2b-1), which has previously been shown to bind specifically to xylan and the other at the C-terminus (CBM2b-2). Biochemical characterization of CBM2b-2 showed that the module bound to insoluble and soluble oat spelt xylan and xylohexaose with K(a) values of 5.6 x 10(4), 1.2 x 10(4), and 4.8 x 10(3) M(-1), respectively, but exhibited extremely weak affinity for cellohexaose (<10(2) M(-1)), and its interaction with insoluble cellulose was too weak to quantify. The CBM did not interact with soluble forms of other plant cell wall polysaccharides. The three-dimensional structure of CBM2b-2 was determined by NMR spectroscopy. The module has a twisted "beta-sandwich" architecture, and the two surface exposed tryptophans, Trp 570 and Trp 602, which are in a perpendicular orientation with each other, were shown to be essential for ligand binding. In addition, changing Arg 573 to glycine altered the polysaccharide binding specificity of the module from xylan to cellulose. These data demonstrate that the biochemical properties and tertiary structure of CBM2b-2 and CBM2b-1 are extremely similar. When CBM2b-1 and CBM2b-2 were incorporated into a single polypeptide chain, either in the full-length enzyme or an artificial construct comprising both CBM2bs covalently joined via a flexible linker, there was an approximate 18-20-fold increase in the affinity of the protein for soluble and insoluble xylan, as compared to the individual modules, and a measurable interaction with insoluble acid-swollen cellulose, although the K(a) (approximately 6.0 x 10(4) M(-1)) was still much lower than for insoluble xylan (K(a) = approximately 1.0 x 10(6) M(-1)). These data demonstrate that the two family 2b CBMs of Cf Xyn11A act in synergy to bind acid swollen cellulose and xylan. We propose that the increased affinity of glycoside hydrolases for polysaccharides, through the synergistic interactions of CBMs, provides an explanation for the duplication of CBMs from the same family in some prokaryotic cellulases and xylanases.