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PDBsum entry 1qw9
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Crystal structure and snapshots along the reaction pathway of a family 51 alpha-L-Arabinofuranosidase.
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Authors
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K.Hövel,
D.Shallom,
K.Niefind,
V.Belakhov,
G.Shoham,
T.Baasov,
Y.Shoham,
D.Schomburg.
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Ref.
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Embo J, 2003,
22,
4922-4932.
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PubMed id
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Abstract
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High-resolution crystal structures of alpha-L-arabinofuranosidase from
Geobacillus stearothermophilus T-6, a family 51 glycosidase, are described. The
enzyme is a hexamer, and each monomer is organized into two domains: a
(beta/alpha)8-barrel and a 12-stranded beta sandwich with jelly-roll topology.
The structures of the Michaelis complexes with natural and synthetic substrates,
and of the transient covalent arabinofuranosyl-enzyme intermediate represent two
stable states in the double displacement mechanism, and allow thorough
examination of the catalytic mechanism. The arabinofuranose sugar is tightly
bound and distorted by an extensive network of hydrogen bonds. The two catalytic
residues are 4.7 A apart, and together with other conserved residues contribute
to the stabilization of the oxocarbenium ion-like transition state via charge
delocalization and specific protein-substrate interactions. The enzyme is an
anti-protonator, and a 1.7 A electrophilic migration of the anomeric carbon
takes place during the hydrolysis.
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