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PDBsum entry 4l2b
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Oxidoreductase
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PDB id
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4l2b
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References listed in PDB file
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Key reference
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Title
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Structural and denaturation studies of two mutants of a cold adapted superoxide dismutase point to the importance of electrostatic interactions in protein stability.
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Authors
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A.Merlino,
I.Russo krauss,
I.Castellano,
M.R.Ruocco,
A.Capasso,
E.De vendittis,
B.Rossi,
F.Sica.
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Ref.
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Biochim Biophys Acta, 2014,
1844,
632-640.
[DOI no: ]
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PubMed id
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Abstract
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A peculiar feature of the psychrophilic iron superoxide dismutase from
Pseudoalteromonas haloplanktis (PhSOD) is the presence in its amino acid
sequence of a reactive cysteine (Cys57). To define the role of this residue, a
structural characterization of the effect of two PhSOD mutations, C57S and C57R,
was performed. Thermal and denaturant-induced unfolding of wild type and mutant
PhSOD followed by circular dichroism and fluorescence studies revealed that
C→R substitution alters the thermal stability and the resistance against
denaturants of the enzyme, whereas C57S only alters the stability of the protein
against urea. The crystallographic data on the C57R mutation suggest an
involvement of the Arg side chain in the formation of salt bridges on protein
surface. These findings support the hypothesis that the thermal resistance of
PhSOD relies on optimization of charge-charge interactions on its surface. Our
study contributes to a deeper understanding of the denaturation mechanism of
superoxide dismutases, suggesting the presence of a structural dimeric
intermediate between the native state and the unfolded state. This hypothesis is
supported by the crystalline and solution data on the reduced form of the enzyme.
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