title: EXAFS studies of Fe(III)-phosvitin at high metal to protein ratios.
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 A. 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.
authors.affiliation: Department of Chemistry, University of Siena, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Mangani
authors.forename: P L
authors.initials: PL
authors.lastname: Orioli
authors.forename: A
authors.initials: A
authors.lastname: Scozzafava
authors.forename: L
authors.initials: L
authors.lastname: Messori
authors.forename: P
authors.initials: P
authors.lastname: Carloni
mesh_terms: D000818:Animals; D001665:Binding Sites; D002645:Chickens; D005290:Ferric Compounds / Q000378:metabolism*; D005583:Fourier Analysis; D008968:Molecular Conformation; D010766:Phosphorylation; D010774:Phosvitin / Q000378:metabolism*; D013057:Spectrum Analysis; D013329:Structure-Activity Relationship; D014965:X-Rays
chemical_list: D005290:Ferric Compounds; D010774:Phosvitin