EXAFS studies of Fe(III)-phosvitin at high metal to protein ratios.
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.
Mangani
S
S
Department of Chemistry, University of Siena, Italy.
Orioli
P L
PL
Scozzafava
A
A
Messori
L
L
Carloni
P
P
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
D005290:Ferric Compounds; D010774:Phosvitin