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PDBsum entry 2b9v
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References listed in PDB file
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Key reference
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Title
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Acetobacter turbidans alpha-Amino acid ester hydrolase: how a single mutation improves an antibiotic-Producing enzyme.
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Authors
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T.R.Barends,
J.J.Polderman-Tijmes,
P.A.Jekel,
C.Williams,
G.Wybenga,
D.B.Janssen,
B.W.Dijkstra.
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Ref.
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J Biol Chem, 2006,
281,
5804-5810.
[DOI no: ]
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PubMed id
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Abstract
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The alpha-amino acid ester hydrolase (AEH) from Acetobacter turbidans is a
bacterial enzyme catalyzing the hydrolysis and synthesis of beta-lactam
antibiotics. The crystal structures of the native enzyme, both unliganded and in
complex with the hydrolysis product D-phenylglycine are reported, as well as the
structures of an inactive mutant (S205A) complexed with the substrate
ampicillin, and an active site mutant (Y206A) with an increased tendency to
catalyze antibiotic production rather than hydrolysis. The structure of the
native enzyme shows an acyl binding pocket, in which D-phenylglycine binds, and
an additional space that is large enough to accommodate the beta-lactam moiety
of an antibiotic. In the S205A mutant, ampicillin binds in this pocket in a
non-productive manner, making extensive contacts with the side chain of
Tyr(112), which also participates in oxyanion hole formation. In the Y206A
mutant, the Tyr(112) side chain has moved with its hydroxyl group toward the
catalytic serine. Because this changes the properties of the beta-lactam binding
site, this could explain the increased beta-lactam transferase activity of this
mutant.
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Figure 2.
a, stereo figure of the A. turbidans α-amino acid ester
hydrolase tetramer. A surface representation is shown, in which
each monomer is individually colored. b, stereo figure of the A.
turbidans α-amino acid ester hydrolase monomer. The arm and
α/β-hydrolase domains are shown in green, the cap domain in
orange, and the jellyroll domain in blue. The side chain of the
active site Ser^205 is shown in space filling representation.
Helices αC-αF and strands β4-β7 are labeled. The figure was
prepared using PYMOL (DeLano Scientific) and Molscript (30).
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Figure 4.
Stereo picture of the 2F[o] - F[c] electron density of
ampicillin in the active site of the S205A mutant, after
refinement of the initial molecular replacement solution, prior
to inclusion of ampicillin in the model. The density was
contoured at 1.0 σ, and overlaid on the final refined
structure. The figure was prepared using Xfit (22) and Raster3D
(32).
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2006,
281,
5804-5810)
copyright 2006.
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