Role of phosphate in initial iron deposition in apoferritin

Journal Article · Tue Mar 19 00:00:00 EST 1991 · Biochemistry; (United States)

DOI:https://doi.org/10.1021/bi00225a031· OSTI ID:5029813

Cheng, Yonghong G; Chasteen, N D ^[1]

---

1. Univ. of New Hampshire, Durham (United States)

Ferritins from microorganisms to man are known to contain varying amounts of phoshate which has a pronounced effect on the structural and magnetic properties of their iron mineral cores. The present study was undertaken to gain insight into the role of phosphate in the early stages of iron accumulation by ferritin. The influence of phosphate on the initial deposition of iron in apoferritin (12 Fe/protein) was investigated by EPR, {sup 57}Fe Mossbauer spectroscopy, and equilibrium dialysis. The results indicate that phosphate has a signigicant influence on iron depositon. Following oxidation, an intermediate mononuclear Fe-(III)-protein complex is formed which exhibits a transient EPR singal at g{prime} {equals} 4.3. Phosphate accelerates the rate of decay of the signal by a factor of 3-4, producing EPR-silent oligonuclear or polynuclear Fe(III) clusters. The mononuclear g{prime} {equals} 4.3 complex may arise from Fe(III) finding at a ferroxidase site or a nucleation site to which the Fe(III) has rapidly migrated following oxidation. Titration data suggest that a 3:1 P{sub i}/Fe(III) complex is formed as the g{prime} = 4.3 EPR signal decays. This complex may play a role in the migration of iron within the protein to form iron clusters, ultimately leading to formation of the core. The clusters can accommodate up to 0.38 {plus minus} 0.03 P{sub i}/Fe as measured by equilibrium dialysis.

• OSTI ID: 5029813
• Journal Information: Biochemistry; (United States), Vol. 30:11; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
FERRITIN
ELECTRON SPIN RESONANCE
SODIUM PHOSPHATES
BIOCHEMISTRY
ELECTRON SPECTRA
IRON 57
IRON COMPOUNDS
OXIDATION
PHOSPHORUS 32
ALKALI METAL COMPOUNDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DAYS LIVING RADIOISOTOPES
EVEN-ODD NUCLEI
INTERMEDIATE MASS NUCLEI
IRON COMPLEXES
IRON ISOTOPES
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
METALLOPROTEINS
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHOSPHORUS ISOTOPES
PROTEINS
RADIOISOTOPES
RESONANCE
SODIUM COMPOUNDS
SPECTRA
STABLE ISOTOPES
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
550201* - Biochemistry- Tracer Techniques