PDBsum entry 3c7g

Hydrolase

PDB id: 3c7g

Contents

Protein chain

488 a.a.

Ligands

XYP-XYP-XYP-XYP

GOL

Metals

_CA

_NA ×2

Waters ×446

References listed in PDB file

Key reference

• Title: Structural analysis of a glycoside hydrolase family 43 arabinoxylan arabinofuranohydrolase in complex with xylotetraose reveals a different binding mechanism compared with other members of the same family.
• Authors: E.Vandermarliere, T.M.Bourgois, M.D.Winn, S.Van campenhout, G.Volckaert, J.A.Delcour, S.V.Strelkov, A.Rabijns, C.M.Courtin.
• Ref.: Biochem J, 2009, 418, 39-47.
• PubMed id: 18980579

Abstract

AXHs (arabinoxylan arabinofuranohydrolases) are alpha-L-arabinofuranosidases that specifically hydrolyse the glycosidic bond between arabinofuranosyl substituents and xylopyranosyl backbone residues of arabinoxylan. Bacillus subtilis was recently shown to produce an AXH that cleaves arabinose units from O-2- or O-3-mono-substituted xylose residues: BsAXH-m2,3 (B. subtilis AXH-m2,3). Crystallographic analysis reveals a two-domain structure for this enzyme: a catalytic domain displaying a five-bladed beta-propeller fold characteristic of GH (glycoside hydrolase) family 43 and a CBM (carbohydrate-binding module) with a beta-sandwich fold belonging to CBM family 6. Binding of substrate to BsAXH-m2,3 is largely based on hydrophobic stacking interactions, which probably allow the positional flexibility needed to hydrolyse both arabinose substituents at the O-2 or O-3 position of the xylose unit. Superposition of the BsAXH-m2,3 structure with known structures of the GH family 43 exo-acting enzymes, beta-xylosidase and alpha-L-arabinanase, each in complex with their substrate, reveals a different orientation of the sugar backbone.