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PDBsum entry 1udp
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References listed in PDB file
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Key reference
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Title
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The molecular structure of udp-Galactose 4-Epimerase from escherichia coli determined at 2.5 a resolution.
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Authors
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A.J.Bauer,
I.Rayment,
P.A.Frey,
H.M.Holden.
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Ref.
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Proteins, 1992,
12,
372-381.
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PubMed id
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Abstract
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UDP-galactose 4-epimerase catalyzes the conversion of UDP-galactose to
UDP-glucose during normal galactose metabolism. The molecular structure of
UDP-galactose 4-epimerase from Escherichia coli has now been solved to a nominal
resolution of 2.5 A. As isolated from E. coli, the molecule is a dimer of
chemically identical subunits with a total molecular weight of 79,000. Crystals
of the enzyme used for this investigation were grown as a complex with the
substrate analogue, UDP-benzene, and belonged to the space group P2(1)2(1)2(1)
with unit cell dimensions of a = 76.3 A, b = 83.1 A, c = 132.1 A, and one dimer
per asymmetric unit. An interpretable electron density map calculated to 2.5 A
resolution was obtained by a combination of multiple isomorphous replacement
with six heavy atom derivatives, molecular averaging, and solvent flattening.
Each subunit of epimerase is divided into two domains. The larger N-terminal
domain, composed of amino acid residues 1-180, shows a classic NAD+ binding
motif with seven strands of parallel beta-pleated sheet flanked on either side
of alpha-helices. The seventh strand of the beta-pleated sheet is contributed by
amino acid residues from the smaller domain. In addition, this smaller
C-terminal domain, consisting of amino acid residues 181-338, contains three
strands of beta-pleated sheet, two major alpha-helices and one helical turn. The
substrate analogue, UDP-benzene, binds in the cleft located between the two
domains with its phenyl ring in close proximity to the nicotinamide ring of
NAD+. Contrary to the extensive biochemical literature suggesting that epimerase
binds only one NAD+ per functional dimer, the map clearly shows electron density
for two nicotinamide cofactors binding in symmetry-related positions in the
dimer. Likewise, each subunit in the dimer also binds one substrate analogue.
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Secondary reference #1
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Title
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The isolation, Purification, And preliminary crystallographic characterization of udp-Galactose-4-Epimerase from escherichia coli.
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Authors
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A.J.Bauer,
I.Rayment,
P.A.Frey,
H.M.Holden.
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Ref.
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Proteins, 1991,
9,
135-142.
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PubMed id
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Headers
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