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PDBsum entry 2c9v
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Oxidoreductase
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PDB id
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2c9v
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References listed in PDB file
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Key reference
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Title
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Variable metallation of human superoxide dismutase: atomic resolution crystal structures of cu-Zn, Zn-Zn and as-Isolated wild-Type enzymes.
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Authors
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R.W.Strange,
S.V.Antonyuk,
M.A.Hough,
P.A.Doucette,
J.S.Valentine,
S.S.Hasnain.
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Ref.
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J Mol Biol, 2006,
356,
1152-1162.
[DOI no: ]
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PubMed id
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Abstract
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Human Cu-Zn superoxide dismutase (SOD1) protects cells from the effects of
oxidative stress. Mutations in SOD1 are linked to the familial form of
amyotrophic lateral sclerosis. Several hypotheses for their toxicity involve the
mis-metallation of the enzyme. We present atomic-resolution crystal structures
and biophysical data for human SOD1 in three metallation states: Zn-Zn, Cu-Zn
and as-isolated. These data represent the first atomic-resolution structures for
human SOD1, the first structure of a reduced SOD1, and the first structure of a
fully Zn-substituted SOD1 enzyme. Recombinantly expressed as-isolated SOD1
contains a mixture of Zn and Cu at the Cu-binding site. The Zn-Zn structure
appears to be at least as stable as the correctly (Cu-Zn) metallated enzyme.
These data raise the possibility that in a cellular environment with low
availability of free copper, Zn-Zn may be the preferred metallation state of
SOD1 prior to its interaction with the copper chaperone.
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Figure 4.
Figure 4. The water network at the active site of the
re-constituted Cu-Zn enzyme, monomer A. A sulphate ion sits on
the surface of the molecule at the substrate entry site. A
dual-occupancy water molecule (W1) is 2.6 Å from Cu(II)
and 3.7 Å from the position of the Cu(I) atom. W1 is
linked to the Thr137 O protein backbone via a H bond and to the
Gly141 O atom via H bonding to a second water molecule, W2,
which is also linked (2.8 Å) to water molecule W3, the
Gly141 residue and to a sulphate ion on the protein surface (2.6
Å). W3 forms a long (2.9 Å) H-bond to the Ny group
of Arg143. A full-occupancy water molecule, W5, is in direct
contact with the protein main chain, linked to the Lys136 O and
His63 N atoms. W5 and W3 are linked by W4, which is 4.4 Å
from Cu(II). The Gly141 O and Arg143 Ne atoms are bridged by W6.
Finally, W7, 5.3 Å from the (Zn site) Zn atom and a highly
conserved water molecule in all three structures (and in bovine
SOD), has H bonds with the secondary bridge residue Asp124 Od
(2.8 Å) and with Gly85 N (2.9 Å) and Gly72 O (2.8 Å) atoms.
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Figure 6.
Figure 6. Thermal probability ellipsoids for the active
sites of the (a) Cu-Zn, (b) as-isolated and (c) Zn-Zn
structures. The sites show only limited anisotropy. The highly
anisotropic ellipsoid for Cu(II) in the Cu-Zn structure is
indicative of a range of positions adopted by the metal ion.
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The above figures are
reprinted
by permission from Elsevier:
J Mol Biol
(2006,
356,
1152-1162)
copyright 2006.
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