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PDBsum entry 1psc
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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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Three-Dimensional structure of the binuclear metal center of phosphotriesterase.
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Authors
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M.M.Benning,
J.M.Kuo,
F.M.Raushel,
H.M.Holden.
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Ref.
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Biochemistry, 1995,
34,
7973-7978.
[DOI no: ]
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PubMed id
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Abstract
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Phosphotriesterase, as isolated from Pseudomonas diminuta, is capable of
detoxifying widely used pesticides such as paraoxon and parathion and various
mammalian acetylcholinesterase inhibitors. The enzyme requires a binuclear metal
center for activity. Recently, the three-dimensional structure of the apoenzyme
was solved (Benning et al., 1994) and shown to consist of an alpha/beta-barrel.
Here we describe the three-dimensional structure of the holoenzyme,
reconstituted with cadmium, as determined by X-ray crystallographic analysis to
2.0-A resolution. Crystals employed in the investigation belonged to the space
group C2 with unit cell dimensions of a = 129.5 A, b = 91.4 A, c = 69.4 A, beta
= 91.9 degrees, and two subunits in the asymmetric unit. There are significant
differences in the three-dimensional architecture of the apo and holo forms of
the enzyme such that their alpha-carbon positions superimpose with a
root-mean-square deviation of 3.4 A. The binuclear metal center is located at
the C-terminus of the beta-barrel with the cadmiums separated by 3.8 A. There
are two bridging ligands to the metals: a water molecule (or possibly a
hydroxide ion) and a carbamylated lysine residue (Lys 169). The more buried
cadmium is surrounded by His 55, His 57, Lys 169, Asp 301, and the bridging
water in a trigonal bipyramidal arrangement. The second metal is coordinated in
a distorted octahedral geometry by His 201, His 230, Lys 169, the bridging water
molecule, and two additional solvents.
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