4L2C: X-ray Structure Of The C57r Mutant Of The Iron Superoxide Dismutase From Pseudoalteromonas Haloplanktis (crystal Form I)

Citation:
Abstract
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.
PDB ID: 4L2CDownload
MMDB ID: 117826
PDB Deposition Date: 2013/6/4
Updated in MMDB: 2014/03
Experimental Method:
x-ray diffraction
Resolution: 1.66  Å
Source Organism:
Similar Structures:
Biological Unit for 4L2C: dimeric; determined by author and by software (PISA)
Molecular Components in 4L2C
Label Count Molecule
Proteins (2 molecules)
2
Superoxide Dismutase [fe]
Molecule annotation
Chemicals (4 molecules)
1
2
2
2
* Click molecule labels to explore molecular sequence information.

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