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PDBsum entry 1fce
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Cellulase degradation
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PDB id
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1fce
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References listed in PDB file
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Key reference
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Title
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The crystal structure of the processive endocellulase celf of clostridium cellulolyticum in complex with a thiooligosaccharide inhibitor at 2.0 a resolution.
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Authors
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G.Parsiegla,
M.Juy,
C.Reverbel-Leroy,
C.Tardif,
J.P.Belaïch,
H.Driguez,
R.Haser.
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Ref.
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EMBO J, 1998,
17,
5551-5562.
[DOI no: ]
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PubMed id
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Abstract
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The mesophilic bacterium Clostridium cellulolyticum exports multienzyme
complexes called cellulosomes to digest cellulose. One of the three major
components of the cellulosome is the processive endocellulase CelF. The crystal
structure of the catalytic domain of CelF in complex with two molecules of a
thiooligosaccharide inhibitor was determined at 2.0 A resolution. This is the
first three-dimensional structure to be solved of a member of the family 48
glycosyl hydrolases. The structure consists of an (alpha alpha)6-helix barrel
with long loops on the N-terminal side of the inner helices, which form a
tunnel, and an open cleft region covering one side of the barrel. One inhibitor
molecule is enclosed in the tunnel, the other exposed in the open cleft. The
active centre is located in a depression at the junction of the cleft and tunnel
regions. Glu55 is the proposed proton donor in the cleavage reaction, while the
corresponding base is proposed to be either Glu44 or Asp230. The orientation of
the reducing ends of the inhibitor molecules together with the chain translation
through the tunnel in the direction of the active centre indicates that CelF
cleaves processively cellobiose from the reducing to the non-reducing end of the
cellulose chain.
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Figure 1.
Figure 1 Chemical structure of the thiooligosaccharide inhibitor
methyl 4-S-  -cellobiosyl-4-thio-cellobioside,
which is called IG4 in this article. The sugar subunits are
labelled from (A) to (D) from the non-reducing to the
O-methylated reducing end.
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Figure 7.
Figure 7 The (2F[o]-F[c]) electron density map contoured at the
1  level,
following the inhibitor molecules Inh1 (-6 to -4) and Inh2 (+1
to +4) from the tunnel to the end of the open cleft. It shows as
well the unexplained density at the gap between the inhibitor
molecules.
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The above figures are
reprinted
from an Open Access publication published by Macmillan Publishers Ltd:
EMBO J
(1998,
17,
5551-5562)
copyright 1998.
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