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PDBsum entry 1lzd
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Hydrolase (o-glycosyl)
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PDB id
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1lzd
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References listed in PDB file
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Key reference
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Title
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Dissection of protein-Carbohydrate interactions in mutant hen egg-White lysozyme complexes and their hydrolytic activity.
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Authors
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K.Maenaka,
M.Matsushima,
H.Song,
F.Sunada,
K.Watanabe,
I.Kumagai.
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Ref.
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J Mol Biol, 1995,
247,
281-293.
[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 were identified by an automated
search of PubMed on title and author
names, giving a
perfect match.
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Abstract
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Trp62 in the binding subsite B of hen egg-white lysozyme shows general features
often observed in protein-carbohydrate interactions including a stacking
interaction and a hydrogen bonding network with water molecules. A previous
report by our group showed that the perturbation of these interactions by
substitution of Trp62 with tyrosine or phenylalanine affects the substrate
binding modes and also enhances the hydrolytic activity. In order to elucidate
the relationship between structural and functional changes of these
protein-carbohydrate interactions, the Trp62Tyr and Trp62Phe mutants complexed
with the substrate analogue, (GlcNAc)3, were analyzed at 1.8 A resolution by
X-ray crystallography. The overall structures of the mutant enzymes are
indistinguishable from that of the wild type enzyme. Although the wild-type
enzyme binds (GlcNAc)3 in only one binding mode (A-B-C), the Trp62Tyr mutant
binds (GlcNAc)3 in two binding modes (A-B-C, B-C-D) and the Trp62Phe mutant has
an even weaker binding mode. The aromatic rings of Tyr62 and Phe62 maintain
their interactions with the carbohydrate molecules, but make fewer stacking
interactions with the GlcNAc in the B site than the wild-type enzyme does. The
hydroxyl group of Tyr62 interacts weakly with a water molecule which mediates
hydrogen bonding in the GlcNAc residues in the B and C sites. The C-6 hydroxyl
group of the GlcNAc residue in the C site rotates around the C-5-C-6 bond to
complete the hydrogen bond network in the Trp62Tyr mutant-(GlcNAc)3 complex. On
the other hand, this hydrogen bonding network does not form in the Trp62Phe
mutant-(GlcNAc)3. In addition to these structural studies, the kinetic
parameters of the hydrolysis of 4-methylumbelliferyl N-acetyl-chitotriose,
((GlcNAc)3-MeU), have been determined in order to further characterize the
enzymatic properties of these mutant lysozymes. This demonstrates that the
modulation of the hydrogen bonding network, including the flexible part of the
carbohydrate and water molecules and/or the slight reduction of stacking
interaction in the B site, alters the binding mode toward the carbohydrate and
induces an enhancement of the hydrolytic activity.
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Figure 4.
Figure 4. The GlcNAc oligomer
binding modes toward the subsites
of the hen egg-white lysozyme and
its mutants are shown together with
the average temperature factors for
each GlcNAc residue (numbers
under the GlcNAc residues). The
Trp62Tyr mutant had a (GlcNAc)3 in
2 binding modes, A-B-C and B-C-D
(see the text).
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Figure 8.
Figure 8. Schematic Figures of the interactions between
lysozyme and the GlcNAc oligomer molecule: (a) WT3, (b)
W62Y3 and (c) W62F3. The dotted lines and numbers
indicate the hydrogen bonds and their distances (in Å ),
respectively.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(1995,
247,
281-293)
copyright 1995.
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