Iron(III) clusters bound to horse spleen apoferritin: an X-ray absorption and Moessbauer spectroscopy study that shows that iron nuclei can form on the protein

Journal Article · Tue Jan 27 00:00:00 EST 1987 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00376a023· OSTI ID:6521688

Yang, C; Meagher, A; Huynh, B H; Sayers, D E; Theil, E C

Ferritin is a complex of a hollow, spherical protein and a hydrous, ferric oxide core of less than or equal to4500 iron atoms inside the apoprotein coat; the apoprotein has multiple binding sites for monoatomic metal ions, e.g., Fe(II), V(IV), Tb(III), that may be important in the initiation of iron core formation. In an earlier study the authors observed that the oxidation of Fe(II) vacated some, but not all, of the metal-binding sites, suggesting migration of some Fe during oxidation, possibly to form nucleation clusters; some Fe(III) remained bound to the protein. Preliminary extended X-ray absorbance fine structure (EXAFS) analysis of the same Fe(III)-apoferritin complex showed an environment distinct from ferritin cores, but the data did not allow a test of the Fe cluster hypothesis. In this paper, with improved EXAFS data and with Moessbauer data on the same complex formed with /sup 57/Fe, they clearly show that the Fe(III) in the distinctive environment is polynuclear. Moreover, the arrangement of atoms is such that Fe(III) atoms appear to have both carboxylate-like ligands, presumably from apoferritin, and oxo bridges to the other iron atoms. Thus the protein provides sites not only for initiation but also for nucleation of the iron core. Sites commodious enough and with sufficient conserved carboxylate ligands to accommodate such a nucleus occur inside the protein coat at the subunit dimer interfaces. Such Fe(III)-apoferritin nucleation complexes can be used to study the properties of the several members of the apoferritin family.

• Research Organization: North Carolina State Univ., Raleigh
• OSTI ID: 6521688
• Journal Information: Biochemistry; (United States), Vol. 26:2
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
FERRITIN
ABSORPTION SPECTRA
MOLECULAR STRUCTURE
X-RAY SPECTROSCOPY
HORSES
IRON 57
IRON OXIDES
SPLEEN
ANIMALS
BODY
CHALCOGENIDES
COMPLEXES
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
IRON COMPLEXES
IRON COMPOUNDS
IRON ISOTOPES
ISOTOPES
MAMMALS
METALLOPROTEINS
NUCLEI
ORGANIC COMPOUNDS
ORGANS
OXIDES
OXYGEN COMPOUNDS
PROTEINS
SPECTRA
SPECTROSCOPY
STABLE ISOTOPES
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics
550602 - Medicine- External Radiation in Diagnostics- (1980-)