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- Title
Comparative Fe and Zn K-edge X-ray absorption spectroscopic study of the ferroxidase centres of human H-chain ferritin and bacterioferritin from Desulfovibrio desulfuricans.
- Authors
Toussaint, L.; Cuypers, M. G.; Bertrand, L.; Hue, L.; Romão, C. V.; Saraiva, L. M.; Teixeira, M.; Meyer-Klaucke, W.; Feiters, M. C.; Crichton, R. R.
- Abstract
Iron uptake by the ubiquitous iron-storage protein ferritin involves the oxidation of two Fe(II) ions located at the highly conserved dinuclear “ferroxidase centre” in individual subunits. We have measured X-ray absorption spectra of four mutants (K86Q, K86Q/E27D, K86Q/E107D, and K86Q/E27D/E107D, involving variations of Glu to Asp on either or both sides of the dinuclear ferroxidase site) of recombinant human H-chain ferritin (rHuHF) in their complexes with reactive Fe(II) and redox-inactive Zn(II). The results for Fe–rHuHf are compared with those for recombinant Desulfovibrio desulfuricans bacterioferritin (DdBfr) in three states: oxidised, reduced, and oxidised/Chelex®-treated. The X-ray absorption near-edge region of the spectrum allows the oxidation state of the iron ions to be assessed. Extended X-ray absorption fine structure simulations have yielded accurate geometric information that represents an important refinement of the crystal structure of DdBfr; most metal–ligand bonds are shortened and there is a decrease in ionic radius going from the Fe(II) to the Fe(III) state. The Chelex®-treated sample is found to be partly mineralised, giving an indication of the state of iron in the cycled-oxidised (reduced, then oxidised) form of DdBfr, where the crystal structure shows the dinuclear site to be only half occupied. In the case of rHuHF the complexes with Zn(II) reveal a surprising similarity between the variants, indicating that the rHuHf dinuclear site is rigid. In spite of this, the rHuHf complexes with Fe(II) show a variation in reactivity that is reflected in the iron oxidation states and coordination geometries.
- Subjects
IRON; FERRITIN; X-ray absorption near edge structure; DESULFOVIBRIO; OXIDATION; SOLUTION (Chemistry)
- Publication
Journal of Biological Inorganic Chemistry (JBIC), 2009, Vol 14, Issue 1, p35
- ISSN
0949-8257
- Publication type
Article
- DOI
10.1007/s00775-008-0422-3