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Lookup NU author(s): Dr James Flint, Professor Rick Lewis, Emeritus Professor Harry Gilbert, Dr James Murray
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Xylan, which is a key component of the plant cell wall, consists of a backbone of β-1,4-linked xylose residues that are decorated with arabinofuranose, acetyl, 4-O-methyl d-glucuronic acid and ferulate. The backbone of xylan is hydrolysed by endo-β1,4-xylanases (xylanases); however, it is unclear whether the various side-chains of the polysaccharide are utilized by these enzymes as significant substrate specificity determinants. To address this question we have determined the crystal structure of a family 10 xylanase from Thermoascus aurantiacus, in complex with xylobiose containing an arabinofuranosyl-ferulate side-chain. We show that the distal glycone subsite of the enzyme makes extensive direct and indirect interactions with the arabinose side-chain, while the ferulate moiety is solvent-exposed. Consistent with the 3D structural data, the xylanase displays fourfold more activity against xylotriose in which the non-reducing moiety is linked to an arabinose side-chain, compared to the undecorated form of the oligosacchairde. These data indicate that the sugar decorations of xylans in the T. aurantiacus family 10 xylanase, rather than simply being accommodated, can be significant substrate specificity determinants. © 2005 Elsevier Ltd. All rights reserved.
Author(s): Vardakou M, Flint JE, Christakopoulos P, Lewis RJ, Gilbert HJ, Murray JW
Publication type: Article
Publication status: Published
Journal: Journal of Molecular Biology
Year: 2005
Volume: 352
Issue: 5
Pages: 1060-1067
Print publication date: 07/10/2005
ISSN (print): 0022-2836
ISSN (electronic): 1089-8638
Publisher: Academic Press
URL: http://dx.doi.org/10.1016/j.jmb.2005.07.051
DOI: 10.1016/j.jmb.2005.07.051
PubMed id: 16140328
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