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|Title:||Exafs Studies of Fe(iii)-phosvitin At High Metal To Protein Ratios||Authors:||Mangani, Stefano
P. L., Orioli
|Keywords:||EXAFS; phosvitin; iron||Issue Date:||1994||Project:||None||Journal:||BIOMETALS||Abstract:||
The stereochemistry of the Fe(III) binding sites in chicken egg phosvitin (PST) at very high iron content, in solution and as a powder, has been investigated through EXAFS spectroscopy. We found that the EXAFS spectra obtained for aqueous PST solutions at metal:protein ratios of 20:1 and 40:1 are very similar to those previously obtained by us on a Fe10PST sample. In all cases the iron ions are octahedrally coordinated by oxygen atoms of the serine-bound phosphate groups and by other ligands from either the protein or the solvent. The average metal-donor atom distance is 1.94 Angstrom. At variance, the EXAFS results for a Fe50PST powder sample suggest the occurrence of a switch in iron coordination from octahedral to lower coordination numbers (5,4). The average iron-oxygen distance is virtually unchanged; apparently, four iron ligands are provided by four different coordinate phosphate groups from the phosphorylated serine residues abundant in the protein. This finding contains interesting implications for the structure-function relationships of this intriguing protein.
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