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Evidence That GH115  -Glucuronidase Activity, Which Is Required to Degrade Plant Biomass, Is Dependent on Conformational Flexibility

DOI: 10.1074/jbc.M113.525295 DOI Help
PMID: 24214982 PMID Help

Authors: A. Rogowski (University of Newcastle Upon Tyne) , A. Basle (University of Newcastle Upon Tyne) , C. S. Farinas (University of Cambridge) , A. Solovyova (University of Newcastle Upon Tyne) , J. C. Mortimer (University of Cambridge) , P. Dupree (University of Cambridge) , H. J. Gilbert (University of Newcastle Upon Tyne) , D. N. Bolam (University of Newcastle Upon Tyne)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry , VOL 289 (1) , PAGES 53 - 64

State: Published (Approved)
Published: January 2014
Diamond Proposal Number(s): 7864

Open Access Open Access

Abstract: The microbial degradation of the plant cell wall is an important biological process that is highly relevant to environmentally significant industries such as the bioenergy and biorefining sectors. A major component of the wall is glucuronoxylan, a β1,4-linked xylose polysaccharide that is decorated with α-linked glucuronic and/or methylglucuronic acid (GlcA/MeGlcA). Recently three members of a glycoside hydrolase family, GH115, were shown to hydrolyze MeGlcA side chains from the internal regions of xylan, an activity that has not previously been described. Here we show that a dominant member of the human microbiota, Bacteroides ovatus, contains a GH115 enzyme, BoAgu115A, which displays glucuronoxylan α-(4-O-methyl)-glucuronidase activity. The enzyme is significantly more active against substrates in which the xylose decorated with GlcA/MeGlcA is flanked by one or more xylose residues. The crystal structure of BoAgu115A revealed a four-domain protein in which the active site, comprising a pocket that abuts a cleft-like structure, is housed in the second domain that adopts a TIM barrel-fold. The third domain, a five-helical bundle, and the C-terminal β-sandwich domain make inter-chain contacts leading to protein dimerization. Informed by the structure of the enzyme in complex with GlcA in its open ring form, in conjunction with mutagenesis studies, the potential substrate binding and catalytically significant amino acids were identified. Based on the catalytic importance of residues located on a highly flexible loop, the enzyme is required to undergo a substantial conformational change to form a productive Michaelis complex with glucuronoxylan.

Journal Keywords: Bacteroides; Biomass; Crystallography; X-Ray; Glycoside; Humans; Plants; Protein; Secondary; Protein; Tertiary; Substrate; Xylans

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: I02-Macromolecular Crystallography , I04-1-Macromolecular Crystallography (fixed wavelength)

Added On: 21/03/2014 15:39

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