Science · 2000 · 184 citations · 35 references
Oxygen reactions at protein diiron sites are central to bioorganic synthesis and biomineralization, yet previously characterized μ‑1,2 peroxodiferric complexes exhibit Fe‑Fe separations of 3.1–4.0 Å. The authors report a 2.53‑Å Fe‑Fe distance in a ferritin μ‑1,2 peroxodiferric intermediate, indicating a triply bridged structure with a small Fe‑O‑O angle that promotes decay to H₂O₂ and diferric precursors rather than substrate oxidation, thereby explaining the dual substrate/cofactor role of diiron sites.
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 (μ-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 μ-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 (∼106° to 107°). This geometry should favor decay of the peroxodiferric complex by the release of H 2 O 2 and μ-oxo or μ-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 O 2 activation).
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Theoretical x-ray absorption fine structure standards
J. J. Rehr, J. Mustre de León, S. I. Zabinsky et al. · Journal of the American Chemical Society · 1991 · 1.6K citations