title: A short Fe-Fe distance in peroxodiferric ferritin: control of Fe substrate versus cofactor decay?
abstract: The reaction of oxygen with protein diiron sites is important in bioorganic syntheses and biomineralization. An unusually short Fe-Fe distance of 2.53 angstroms was found in the diiron (mu-1,2 peroxodiferric) intermediate that forms in the early steps of ferritin biomineralization. This distance suggests the presence of a unique triply bridged structure. The Fe-Fe distances in the mu-1, 2 peroxodiferric complexes that were characterized previously are much longer (3.1 to 4.0 angstroms). The 2.53 angstrom Fe-Fe distance requires a small Fe-O-O angle (approximately 106 degrees to 107 degrees). This geometry should favor decay of the peroxodiferric complex by the release of H2O2 and mu-oxo or mu-hydroxo diferric biomineral precursors rather than by oxidation of the organic substrate. Geometrical differences may thus explain how diiron sites can function either as a substrate (in ferritin biomineralization) or as a cofactor (in O2 activation).
authors.affiliation: Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA.
authors.forename: J
authors.initials: J
authors.lastname: Hwang
authors.forename: C
authors.initials: C
authors.lastname: Krebs
authors.forename: B H
authors.initials: BH
authors.lastname: Huynh
authors.forename: D E
authors.initials: DE
authors.lastname: Edmondson
authors.forename: E C
authors.initials: EC
authors.lastname: Theil
authors.forename: J E
authors.initials: JE
authors.lastname: Penner-Hahn
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005290:Ferric Compounds / Q000737:chemistry / Q000378:metabolism*; D005293:Ferritins / Q000737:chemistry / Q000378:metabolism*; D005296:Ferrous Compounds / Q000737:chemistry / Q000378:metabolism*; D005583:Fourier Analysis; D010100:Oxygen / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015204:Spectroscopy, Mossbauer; D013057:Spectrum Analysis; D013816:Thermodynamics; D014965:X-Rays
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D011994:Recombinant Proteins; D005293:Ferritins; D010100:Oxygen