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Structural studies by X-ray diffraction on metal substituted desulforedoxin, a rubredoxin-type protein.
M Archer1, A L Carvalho, S Teixeira
1Departamento de Química, Centro de Química Fina e Biotechnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, Portugal.
Protein Science : a Publication of the Protein Society
|July 28, 1999
Summary
Desulforedoxin, a bacterial protein, was studied with various metal substitutions. Structural analysis revealed conserved protein folds but altered metal coordination, offering insights into biological metal centers.
Area of Science:
- Bioinorganic Chemistry
- Structural Biology
- Biophysics
Background:
- Desulforedoxin (Dx) from Desulfovibrio gigas is a small, homodimeric protein.
- Its active center features a high-spin iron atom coordinated by four cysteinyl sulfur atoms, resembling rubredoxin.
- The simple active site and metal-exchange potential make Dx a model for studying metal coordination.
Purpose of the Study:
- To investigate the structural consequences of replacing iron with other metals in Desulforedoxin.
- To explore Dx as a model compound for mimicking biological metal coordination environments.
- To understand metal-ligand interactions within the Dx active site.
Main Methods:
- Metal replacement experiments using In3+, Ga3+, Cd2+, Hg2+, and Ni2+ salts.
- Crystallographic analysis of native and metal-substituted Desulforedoxin derivatives.
- Structure determination using molecular replacement for novel crystal forms.
Main Results:
- In3+ and Ga3+ derivatives were isomorphous with the native iron protein.
- Cd2+, Hg2+, and Ni2+ substituted Dx crystallized in different forms, requiring molecular replacement.
- Structural comparisons showed conserved overall protein structure but variations in metal-sulfur bond lengths and angles.
Conclusions:
- The secondary and tertiary structures of Desulforedoxin remain largely intact upon metal substitution.
- Differences in metal coordination geometry provide insights into the entatic state theory.
- Dx serves as a valuable system for studying the bioinorganic chemistry of metal-sulfur coordination.