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PDBsum entry 1dex
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Rhamnogalacturonan acetylesterase elucidates the structure and function of a new family of hydrolases.
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Authors
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A.Mølgaard,
S.Kauppinen,
S.Larsen.
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Ref.
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Structure, 2000,
8,
373-383.
[DOI no: ]
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PubMed id
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Abstract
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BACKGROUND: The complex polysaccharide rhamnogalacturonan constitutes a major
part of the hairy region of pectin. It can have different types of carbohydrate
sidechains attached to the rhamnose residues in the backbone of alternating
rhamnose and galacturonic acid residues; the galacturonic acid residues can be
methylated or acetylated. Aspergillus aculeatus produces enzymes that are able
to perform a synergistic degradation of rhamnogalacturonan. The deacetylation of
the backbone by rhamnogalacturonan acetylesterase (RGAE) is an essential
prerequisite for the subsequent action of the enzymes that cleave the glycosidic
bonds. RESULTS: The structure of RGAE has been determined at 1.55 A resolution.
RGAE folds into an alpha/beta/alpha structure. The active site of RGAE is an
open cleft containing a serine-histidine-aspartic acid catalytic triad. The
position of the three residues relative to the central parallel beta sheet and
the lack of the nucleophilic elbow motif found in structures possessing the
alpha/beta hydrolase fold show that RGAE does not belong to the alpha/beta
hydrolase family. CONCLUSIONS: Structural and sequence comparisons have revealed
that, despite very low sequence similarities, RGAE is related to seven other
proteins. They are all members of a new hydrolase family, the SGNH-hydrolase
family, which includes the carbohydrate esterase family 12 as a distinct
subfamily. The SGNH-hydrolase family is characterised by having four conserved
blocks of residues, each with one completely conserved residue; serine, glycine,
asparagine and histidine, respectively. Each of the four residues plays a role
in the catalytic function.
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Figure 6.
Figure 6. The orientation of the catalytic triad residues
with respect to the overall fold. (a) Schematic diagram of the
structure of dienelactone hydrolase (PDB accession number 1din)
[43], an a/b hydrolase, viewed from the N-terminal side of the
central b sheet. The three catalytic residues align roughly
parallel to the central b sheet. (b) RGAE viewed from a similar
orientation. The catalytic residues align almost perpendicular
to the central b sheet. The figure was prepared using the
program MOLSCRIPT [42].
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The above figure is
reprinted
by permission from Cell Press:
Structure
(2000,
8,
373-383)
copyright 2000.
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Secondary reference #1
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Title
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Molecular cloning and characterization of a rhamnogalacturonan acetylesterase from aspergillus aculeatus. Synergism between rhamnogalacturonan degrading enzymes.
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Authors
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S.Kauppinen,
S.Christgau,
L.V.Kofod,
T.Halkier,
K.Dörreich,
H.Dalbøge.
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Ref.
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J Biol Chem, 1995,
270,
27172-27178.
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PubMed id
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Secondary reference #2
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Title
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Crystallization and preliminary X-Ray diffraction studies of the heterogeneously glycosylated enzyme rhamnogalacturonan acetylesterase from aspergillus aculeatus.
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Authors
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A.Molgaard,
J.F.Petersen,
S.Kauppinen,
H.Dalbøge,
A.H.Johnsen,
J.C.Navarro poulsen,
S.Larsen.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 1998,
54,
1026-1029.
[DOI no: ]
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PubMed id
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Figure 1.
Fig. 1. Crystals of rRGAE in two of its polymorphic modifications, the
trigonal and the initial orthorhombic, grown under the conditions
19% PEG 4000, 18% 2-propanol, 0.1 M citrate buffer, pH 4.7 and
40 OD280 rRGAE. The length of the orthorhombic crystal is
~1.2 mm.
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The above figure is
reproduced from the cited reference
with permission from the IUCr
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