1oaj: Difference between revisions
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==Overview== | ==Overview== | ||
The influence of the constitutive metal ions on the equilibrium properties, of dimeric Photobacterium leiognathi Cu,Zn superoxide dismutase has been, studied for the wild-type and for two mutant protein forms bearing a, negative charge in the amino acid clusters at the dimer association, interface. Depletion of copper and zinc dissociates the two mutant, proteins into monomers, which reassemble toward the dimeric state upon, addition of stoichiometric amounts of zinc. Pressure-dependent, dissociation is observed for the copper-depleted wild-type and mutated, enzymes, as monitored by the fluorescence shift of a unique tryptophan, residue located at the subunit association interface. The spectral shift, occurs slowly, reaching a plateau after 15-20 minutes, and is fully, reversible. The ... | The influence of the constitutive metal ions on the equilibrium properties, of dimeric Photobacterium leiognathi Cu,Zn superoxide dismutase has been, studied for the wild-type and for two mutant protein forms bearing a, negative charge in the amino acid clusters at the dimer association, interface. Depletion of copper and zinc dissociates the two mutant, proteins into monomers, which reassemble toward the dimeric state upon, addition of stoichiometric amounts of zinc. Pressure-dependent, dissociation is observed for the copper-depleted wild-type and mutated, enzymes, as monitored by the fluorescence shift of a unique tryptophan, residue located at the subunit association interface. The spectral shift, occurs slowly, reaching a plateau after 15-20 minutes, and is fully, reversible. The recovery of the original fluorescence properties, after, decompression, is fast (less than four minutes), suggesting that the, isolated subunit has a relatively stable structure, and excluding the, presence of stable intermediates during the dimer-monomer transition. The, dimer dissociation process is still incomplete at 6.5 kbar for the, copper-depleted wild-type and mutated enzymes, at variance with what is, generally observed for oligomeric proteins that dissociate below 3 kbar., Measurement of the degree of dissociation, at two different protein, concentrations, allows us to calculate the standard volume variation upon, association, Delta V, and the dissociation constant K(d0), at atmospheric, pressure, (25 ml/mol and 3 x 10(-7)M, respectively). The holoprotein is, fully dimeric even at 6.5 kbar, which allows us to evaluate a lower Delta, G degrees limit of 11.5 kcal/mol, corresponding to a dissociation constant, K(d0)<10(-9)M. | ||
==About this Structure== | ==About this Structure== | ||
1OAJ is a | 1OAJ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Photobacterium_leiognathi Photobacterium leiognathi] with ZN and CU as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [http://en.wikipedia.org/wiki/Superoxide_dismutase Superoxide dismutase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=1.15.1.1 1.15.1.1] Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1OAJ OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: zn superoxide dismutase]] | [[Category: zn superoxide dismutase]] | ||
''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 5 14:19:23 2007'' | ||
Revision as of 15:14, 5 November 2007
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ACTIVE SITE COPPER AND ZINC IONS MODULATE THE QUATERNARY STRUCTURE OF PROKARYOTIC CU,ZN SUPEROXIDE DISMUTASE
OverviewOverview
The influence of the constitutive metal ions on the equilibrium properties, of dimeric Photobacterium leiognathi Cu,Zn superoxide dismutase has been, studied for the wild-type and for two mutant protein forms bearing a, negative charge in the amino acid clusters at the dimer association, interface. Depletion of copper and zinc dissociates the two mutant, proteins into monomers, which reassemble toward the dimeric state upon, addition of stoichiometric amounts of zinc. Pressure-dependent, dissociation is observed for the copper-depleted wild-type and mutated, enzymes, as monitored by the fluorescence shift of a unique tryptophan, residue located at the subunit association interface. The spectral shift, occurs slowly, reaching a plateau after 15-20 minutes, and is fully, reversible. The recovery of the original fluorescence properties, after, decompression, is fast (less than four minutes), suggesting that the, isolated subunit has a relatively stable structure, and excluding the, presence of stable intermediates during the dimer-monomer transition. The, dimer dissociation process is still incomplete at 6.5 kbar for the, copper-depleted wild-type and mutated enzymes, at variance with what is, generally observed for oligomeric proteins that dissociate below 3 kbar., Measurement of the degree of dissociation, at two different protein, concentrations, allows us to calculate the standard volume variation upon, association, Delta V, and the dissociation constant K(d0), at atmospheric, pressure, (25 ml/mol and 3 x 10(-7)M, respectively). The holoprotein is, fully dimeric even at 6.5 kbar, which allows us to evaluate a lower Delta, G degrees limit of 11.5 kcal/mol, corresponding to a dissociation constant, K(d0)<10(-9)M.
About this StructureAbout this Structure
1OAJ is a Single protein structure of sequence from Photobacterium leiognathi with ZN and CU as ligands. Active as Superoxide dismutase, with EC number 1.15.1.1 Structure known Active Site: AC1. Full crystallographic information is available from OCA.
ReferenceReference
Active-site copper and zinc ions modulate the quaternary structure of prokaryotic Cu,Zn superoxide dismutase., Cioni P, Pesce A, Morozzo della Rocca B, Castelli S, Falconi M, Parrilli L, Bolognesi M, Strambini G, Desideri A, J Mol Biol. 2003 Mar 7;326(5):1351-60. PMID:12595249
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