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PDBsum entry 1upc
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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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Crystal structure and mechanistic implications of n2-(2-Carboxyethyl)arginine synthase, The first enzyme in the clavulanic acid biosynthesis pathway.
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Authors
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M.E.Caines,
J.M.Elkins,
K.S.Hewitson,
C.J.Schofield.
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Ref.
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J Biol Chem, 2004,
279,
5685-5692.
[DOI no: ]
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PubMed id
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Abstract
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The initial step in the biosynthesis of the clinically important beta-lactamase
inhibitor clavulanic acid involves condensation of two primary metabolites,
D-glyceraldehyde 3-phosphate and L-arginine, to give
N2-(2-carboxyethyl)arginine, a beta-amino acid. This unusual N-C bond forming
reaction is catalyzed by the thiamin diphosphate (ThP2)-dependent enzyme
N2-(2-carboxyethyl)arginine synthase. Here we report the crystal structure of
N2-(2-carboxyethyl)arginine synthase, complexed with ThP2 and Mg2+, to 2.35-A
resolution. The structure was solved in two space groups, P2(1)2(1)2(1) and
P2(1)2(1)2. In both, the enzyme is observed in a tetrameric form, composed of a
dimer of two more tightly associated dimers, consistent with both mass
spectrometric and gel filtration chromatography studies. Both ThP2 and Mg2+
cofactors are present at the active site, with ThP2 in a "V" conformation as in
related enzymes. A sulfate anion is observed in the active site of the enzyme in
a location proposed as a binding site for the phosphate group of the
d-glyceraldehyde 3-phosphate substrate. The mechanistic implications of the
active site arrangement are discussed, including the potential role of the
aminopyrimidine ring of the ThP2. The structure will form a basis for future
mechanistic and structural studies, as well as engineering aimed at production
of alternative beta-amino acids.
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Figure 1.
FIG. 1. Biosynthetic pathway leading to clavulanic acid.
BLS,  -lactam synthetase; PAH,
proclavaminate amidino hydrolase; CAS, clavaminic synthase; CAD,
clavaldehyde dehydrogenase; 2-OG, 2-oxoglutarate.
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Figure 2.
FIG. 2. Structure of the CEAS tetramer. The ThP[2]
molecules are shown as a ball-and-stick representation.
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The above figures are
reprinted
by permission from the ASBMB:
J Biol Chem
(2004,
279,
5685-5692)
copyright 2004.
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