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PDBsum entry 2e4t
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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 of cel44a, A glycoside hydrolase family 44 endoglucanase from clostridium thermocellum.
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Authors
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Y.Kitago,
S.Karita,
N.Watanabe,
M.Kamiya,
T.Aizawa,
K.Sakka,
I.Tanaka.
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Ref.
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J Biol Chem, 2007,
282,
35703-35711.
[DOI no: ]
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PubMed id
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Note: In the PDB file this reference is
annotated as "TO BE PUBLISHED". The citation details given above have
been manually determined.
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Abstract
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The crystal structure of Cel44A, which is one of the enzymatic components of the
cellulosome of Clostridium thermocellum, was solved at a resolution of 0.96 A.
This enzyme belongs to glycoside hydrolase family (GH family) 44. The structure
reveals that Cel44A consists of a TIM-like barrel domain and a beta-sandwich
domain. The wild-type and the E186Q mutant structures complexed with substrates
suggest that two glutamic acid residues, Glu(186) and Glu(359), are the active
residues of the enzyme. Biochemical experiments were performed to confirm this
idea. The structural features indicate that GH family 44 belongs to clan GH-A
and that the reaction catalyzed by Cel44A is retaining type hydrolysis. The
stereochemical course of hydrolysis was confirmed by a (1)H NMR experiment using
the reduced cellooligosaccharide as a substrate.
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Figure 2.
a, the reaction product recognition of the minus subsite
observed with F[o] – F[c] electron density map contoured 2.0σ
in the wild-type crystal structure complexed with cellohexaose.
b, the substrate-recognizing residues and four hydrogen bonds
between the reaction product and the wild-type Cel44A molecule
in the crystal structure. c, close up stereoview of the reducing
end pyranose ring. The F[o] – F[c] electron density map is
shown as a gray surface contoured 2.0σ. The map is shown in the
region of 3.0 Å distance around the substrate in a and c.
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Figure 5.
The F[o] – F[c] electron density map contoured at 2.2σ
around subsite –1 in the E186Q mutant complexed with a high
concentration of cellohexaose. The map is shown in the region of
3.0 Å distance around the substrate. Shown is the model of
the E186Q mutant structure complexed with a high concentration
of cellohexaose.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2007,
282,
35703-35711)
copyright 2007.
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