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PDBsum entry 1i2r
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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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Identification of catalytically important residues in the active site of escherichia coli transaldolase.
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Authors
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U.Schörken,
S.Thorell,
M.Schürmann,
J.Jia,
G.A.Sprenger,
G.Schneider.
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Ref.
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Eur J Biochem, 2001,
268,
2408-2415.
[DOI no: ]
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PubMed id
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Abstract
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The roles of invariant residues at the active site of transaldolase B from
Escherichia coli have been probed by site-directed mutagenesis. The mutant
enzymes D17A, N35A, E96A, T156A, and S176A were purified from a talB-deficient
host and analyzed with respect to their 3D structure and kinetic behavior. X-ray
analysis showed that side chain replacement did not induce unanticipated
structural changes in the mutant enzymes. Three mutations, N35A, E96A, and T156A
resulted mainly in an effect on apparent kcat, with little changes in apparent
Km values for the substrates. Residues N35 and T156 are involved in the
positioning of a catalytic water molecule at the active site and the side chain
of E96 participates in concert with this water molecule in proton transfer
during catalysis. Substitution of Ser176 by alanine resulted in a mutant enzyme
with 2.5% residual activity. The apparent Km value for the donor substrate,
fructose 6-phosphate, was increased nearly fivefold while the apparent Km value
for the acceptor substrate, erythrose 4-phosphate remained unchanged, consistent
with a function for S176 in the binding of the C1 hydroxyl group of the donor
substrate. The mutant D17A showed a 300-fold decrease in kcat, and a fivefold
increase in the apparent Km value for the acceptor substrate erythrose
4-phosphate, suggesting a role of this residue in carbon-carbon bond cleavage
and stabilization of the carbanion/enamine intermediate.
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Figure 2.
Fig. 2. Stereo views of the final 2|Fo|-|Fc| electron
density maps, contoured at 1  , of the
transaldolase mutants D17A (A) and S176A (B).
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Figure 4.
Fig. 4. Proposed reaction mechanism of transaldolase. The
steps leading to the central carbanion/enamine intermediate are
shown. The second half of the reaction, the addition of the
acceptor substrate is in principle the reverse of the first half
of the catalytic cycle and is therefore not included in the
figure. For sake of clarity, only conserved amino-acid side
chains proposed to participate in proton transfer during the
reaction are shown.
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The above figures are
reprinted
by permission from the Federation of European Biochemical Societies:
Eur J Biochem
(2001,
268,
2408-2415)
copyright 2001.
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Secondary reference #1
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Title
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Crystallization and preliminary X-Ray crystallographic analysis of recombinant transaldolase b from eschericha coli.
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Authors
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J.Jia,
Y.Lindqvist,
G.Schneider,
U.Schörken,
H.Sahm,
G.A.Sprenger.
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Ref.
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Acta Crystallogr D Biol Crystallogr, 1996,
52,
192-193.
[DOI no: ]
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PubMed id
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Figure 3.
Fig. 3. Section of the native Patterson map at x = 0.0. The peak height
of the maximum at y = 0.5, z = 0.136 corresponds to 42% of the
origin peak.
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The above figure is
reproduced from the cited reference
with permission from the IUCr
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Secondary reference #2
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Title
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Crystal structure of transaldolase b from escherichia coli suggests a circular permutation of the alpha/beta barrel within the class i aldolase family.
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Authors
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J.Jia,
W.Huang,
U.Schörken,
H.Sahm,
G.A.Sprenger,
Y.Lindqvist,
G.Schneider.
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Ref.
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Structure, 1996,
4,
715-724.
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PubMed id
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Secondary reference #3
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Title
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Crystal structure of the reduced schiff-Base intermediate complex of transaldolase b from escherichia coli: mechanistic implications for class i aldolases.
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Authors
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J.Jia,
U.Schörken,
Y.Lindqvist,
G.A.Sprenger,
G.Schneider.
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Ref.
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Protein Sci, 1997,
6,
119-124.
[DOI no: ]
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PubMed id
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Secondary reference #4
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Title
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The three-Dimensional structure of human transaldolase.
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Authors
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S.Thorell,
P.Gergely,
K.Banki,
A.Perl,
G.Schneider.
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Ref.
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FEBS Lett, 2000,
475,
205-208.
[DOI no: ]
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PubMed id
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Figure 2.
Fig. 2. Schematic view of the transaldolase monomer. The
four most immunodominant peptide stretches in MS patients are
shown in red and residue numbers are given. The side chains
participating in the invariant hydrophobic cluster are shown in
magenta. The figure was generated with Bobscript [24] and
Raster3d [25].
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Figure 3.
Fig. 3. Superposition of the Cα traces of human (gray) and
E. coli (black) transaldolase. The labels indicate the peptide
segments which differ most in structure between the two enzymes.
The figure was generated using the programs Bobscript [24] and
Raster3d [25].
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The above figures are
reproduced from the cited reference
with permission from the Federation of European Biochemical Societies
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