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PDBsum entry 2c7f
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References listed in PDB file
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Key reference
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Title
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Structural insight into the ligand specificity of a thermostable family 51 arabinofuranosidase, Araf51, From clostridium thermocellum.
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Authors
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E.J.Taylor,
N.L.Smith,
J.P.Turkenburg,
S.D'Souza,
H.J.Gilbert,
G.J.Davies.
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Ref.
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Biochem J, 2006,
395,
31-37.
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PubMed id
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Abstract
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The digestion of the plant cell wall requires the concerted action of a diverse
repertoire of enzyme activities. An important component of these hydrolase
consortia are arabinofuranosidases, which release L-arabinofuranose moieties
from a range of plant structural polysaccharides. The anaerobic bacterium
Clostridium thermocellum, a highly efficient plant cell wall degrader, possesses
a single alpha-L-arabinofuranosidase (EC 3.2.1.55), CtAraf51A, located in GH51
(glycoside hydrolase family 51). The crystal structure of the enzyme has been
solved in native form and in 'Michaelis' complexes with both alpha-1,5-linked
arabinotriose and alpha-1,3 arabinoxylobiose, both forming a hexamer in the
asymmetric unit. Kinetic studies reveal that CtAraf51A, in contrast with
well-characterized GH51 enzymes including the Cellvibrio japonicus enzyme
[Beylot, McKie, Voragen, Doeswijk-Voragen and Gilbert (2001) Biochem. J. 358,
607-614], catalyses the hydrolysis of alpha-1,5-linked arabino-oligosaccharides
and the alpha-1,3 arabinosyl side chain decorations of xylan with equal
efficiency. The paucity of direct hydrogen bonds with the aglycone moiety and
the flexible conformation adopted by Trp(178), which stacks against the sugar at
the +1 subsite, provide a structural explanation for the plasticity in substrate
specificity displayed by the clostridial arabinofuranosidase.
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