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PDBsum entry 1u3n
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Unknown function
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PDB id
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1u3n
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References listed in PDB file
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Key reference
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Title
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A prokaryotic superoxide dismutase paralog lacking two cu ligands: from largely unstructured in solution to ordered in the crystal.
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Authors
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L.Banci,
I.Bertini,
V.Calderone,
F.Cramaro,
R.Del conte,
A.Fantoni,
S.Mangani,
A.Quattrone,
M.S.Viezzoli.
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Ref.
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Proc Natl Acad Sci U S A, 2005,
102,
7541-7546.
[DOI no: ]
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PubMed id
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Abstract
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Little is known about prokaryotic homologs of Cu,Zn superoxide dismutase (SOD),
an enzyme highly conserved among eukaryotic species. In 138 Archaea and Bacteria
genomes, 57 of these putative homologs were found, 11 of which lack at least one
of the metal ligands. Both the solution and the crystal structures of the
SOD-like protein from Bacillus subtilis, lacking two Cu ligands and found to be
enzymatically inactive, were determined. In solution, the protein is monomeric.
The available nuclear Overhauser effects, together with chemical-shift index
values, allowed us to define and to recognize the typical Cu,Zn SOD Greek
beta-barrel but with largely unstructured loops (which, therefore, sample a wide
range of conformations). On the contrary, in the crystal structure (obtained in
the presence of slight excess of Zn), the protein is well structured and
organized in covalent dimers held by a symmetric bridge consisting of a Zn ion
bound to an Asp-His dyad in a tetrahedral geometry. Couples of dimers held by
hydrophobic interactions and H bonds are further organized in long chains. The
order/disorder transition is discussed in terms of metal binding and physical
state.
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Figure 2.
Fig. 2. Quaternary structure of BsSOD in the crystal. The
Zn ions are shown as red spheres, and Cl ions are shown as
yellow spheres. The view is approximately down the
noncrystallographic twofold axis passing through the exogenous
Zn.
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Figure 4.
Fig. 4. Comparison between BsSOD and HSOD structures. (A)
The native metal-binding sites of BsSOD (green) and HSOD (red).
Only the BsSOD residues are labeled. The Cl anion is shown as a
yellow sphere. (B) BsSOD (green) and HSOD (red) monomers,
highlighting the conformational differences present in the loop,
are compared. The Zn ions and the Cl anion bound are shown as
red and yellow spheres, respectively.
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