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Title
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Purification, crystallization and preliminary X-ray characterization of the pentamodular arabinoxylanase CtXyl5A from Clostridium thermocellum.
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Authors
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J.L.Brás,
M.A.Correia,
M.J.Romão,
J.A.Prates,
C.M.Fontes,
S.Najmudin.
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Ref.
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Acta Crystallogr Sect F Struct Biol Cryst Commun, 2011,
67,
833-836.
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PubMed id
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Abstract
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The cellulosome, a highly elaborate extracellular multi-enzyme complex of
cellulases and hemicellulases, is responsible for the degradation of plant cell
walls. The xylanase CtXyl5A (Cthe_2193) is a multimodular arabinoxylanase which
is one of the largest components of the Clostridium thermocellum cellulosome.
The N-terminal catalytic domain of CtXyl5A, which is a member of glycoside
hydrolase family 5 (GH5), is responsible for the hydrolysis of arabinoxylans.
Appended after it are three noncatalytic carbohydrate-binding modules (CBMs),
which belong to families 6 (CBM6), 13 (CBM13) and 62 (CBM62). In addition,
CtXyl5A has a fibronectin type III-like (Fn3) module preceding the CBM62 and a
type I dockerin (DOK) module following it which allows the enzyme to be
integrated into the cellulosome through binding to a cohesin module of the
protein scaffold CipA. Crystals of the pentamodular enzyme without the DOK
module at the C-terminus, with the domain architecture
CtGH5-CBM6-CBM13-Fn3-CBM62, have been obtained. The structure of this
pentamodular xylanase has been determined by molecular replacement to a
resolution of 2.64 Å using coordinates of CtGH5-CBM6, Fn3 and CBM62 from the
PDB as search models.
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