Mössbauer spectroscopic study of the initial stages of iron-core formation in horse spleen apoferritin: evidence for both isolated Fe(III) atoms and oxo-bridged Fe(III) dimers as early intermediates.
Abstract: Ferritin stores iron within a hollow protein shell as a polynuclear Fe(III) hydrous oxide core. Although iron uptake into ferritin has been studied previously, the early stages in the creation of the core need to be clarified. These are dealt with in this paper by using Mössbauer spectroscopy, a technique that enables several types of Fe(II) and Fe(III) to be distinguished. Systematic Mössbauer studies were performed on samples prepared by adding 57Fe(II) atoms to apoferritin as a function of pH (5.6-7.0), n [the number of Fe/molecule (4-480)], and tf (the time the samples were held at room temperature before freezing). The measurements made at 4.1 and 90 K showed that for samples with n less than or equal to 40 at pH greater than or equal to 6.25 all iron was trivalent at tf = 3 min. Four different Fe(III) species were identified: solitary Fe(III) atoms giving relaxation spectra, which can be identified with the species observed before by EPR and UV difference spectroscopy; oxo-bridged dimers giving doublet spectra with large splitting, observed for the first time in ferritin; small Fe(III) clusters giving doublets of smaller splitting and larger antiferromagnetically coupled Fe(III) clusters, similar to those found previously in larger ferritin iron cores, which, for samples with n greater than or equal to 40, gave magnetically split spectra at 4.1 K. Both solitary Fe(III) and dimers diminished with time, suggesting that they are intermediates in the formation of the iron core. Two kinds of divalent iron were distinguished for n = 480, which may correspond to bound and free Fe(II).
Publication Date: 1989-06-27 PubMed ID: 2775718DOI: 10.1021/bi00439a025Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
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This study used a technique called Mössbauer spectroscopy to investigate the early stages of iron core formation within ferritin, a protein found in horse spleen. The researchers found evidence of both isolated Fe(III) atoms and oxo-bridged Fe(III) dimers as intermediates in this process.
Overview of the Study
- The study investigates the initial formation of the iron core within ferritin, a protein that stores iron in the body. This process was examined in the spleen of a horse.
- The researchers used a technique called Mössbauer spectroscopy, which allows them to distinguish between different types of iron.
- The research team systematically performed Mössbauer studies under varying conditions, such as pH levels, the number of iron molecules, and the time samples were maintained at room temperature before freezing.
Findings and Observations
- The studies were carried out at two distinct temperatures: 4.1 and 90 Kelvin (K). The results revealed that for samples containing an iron molecule count of less than or equal to 40 at pH values greater than or equal to 6.25, all iron was found to be trivalent when the samples were held at room temperature for 3 minutes.
- The researchers identified four different Fe(III) species: solitary Fe(III) atoms, oxo-bridged dimers, small Fe(III) clusters, and larger antiferromagnetically coupled Fe(III) clusters. This is significant because solitary Fe(III) atoms and oxo-bridged dimers were detected for the first time in ferritin.
- The numbers of both solitary Fe(III) atoms and oxo-bridged dimers decreased over time, which suggests that they act as intermediates in the formation of the iron core within ferritin.
- When the molecule count was 480, two types of divalent iron were identified. The researchers hypothesized that these could correlate to bound and free iron.
Conclusion and Significance
- This research provides critical insight into the early stages of iron core development within ferritin, specifically highlighting the role of distinct types of iron molecules. These findings could have broader implications for understanding iron metabolism in biological systems.
- The study could motivate further investigation into the role of Fe(III) atoms and oxo-bridged dimers in various biological and chemical processes.
Cite This Article
APA
Bauminger ER, Harrison PM, Nowik I, Treffry A.
(1989).
Mössbauer spectroscopic study of the initial stages of iron-core formation in horse spleen apoferritin: evidence for both isolated Fe(III) atoms and oxo-bridged Fe(III) dimers as early intermediates.
Biochemistry, 28(13), 5486-5493.
https://doi.org/10.1021/bi00439a025 Publication
Researcher Affiliations
- Racah Institute of Physics, Hebrew University, Jerusalem, Israel.
MeSH Terms
- Animals
- Apoferritins / metabolism
- Ferritins / analogs & derivatives
- Ferritins / metabolism
- Horses
- Iron / metabolism
- Iron Isotopes
- Kinetics
- Protein Binding
- Spectrum Analysis / methods
- Spleen / metabolism
- Thermodynamics
Grant Funding
- Wellcome Trust
Citations
This article has been cited 11 times.- Pereira AS, Timóteo CG, Guilherme M, Folgosa F, Naik SG, Duarte AG, Huynh BH, Tavares P. Spectroscopic evidence for and characterization of a trinuclear ferroxidase center in bacterial ferritin from Desulfovibrio vulgaris Hildenborough.. J Am Chem Soc 2012 Jul 4;134(26):10822-32.
- Bou-Abdallah F, Papaefthymiou GC, Scheswohl DM, Stanga SD, Arosio P, Chasteen ND. mu-1,2-Peroxobridged di-iron(III) dimer formation in human H-chain ferritin.. Biochem J 2002 May 15;364(Pt 1):57-63.
- Cavallo S, Mei G, Stefanini S, Rosato N, Finazzi-Agrò A, Chiancone E. Formation and movement of Fe(III) in horse spleen, H- and L-recombinant ferritins. A fluorescence study.. Protein Sci 1998 Feb;7(2):427-32.
- Levi S, Santambrogio P, Corsi B, Cozzi A, Arosio P. Evidence that residues exposed on the three-fold channels have active roles in the mechanism of ferritin iron incorporation.. Biochem J 1996 Jul 15;317 ( Pt 2)(Pt 2):467-73.
- Santambrogio P, Levi S, Cozzi A, Corsi B, Arosio P. Evidence that the specificity of iron incorporation into homopolymers of human ferritin L- and H-chains is conferred by the nucleation and ferroxidase centres.. Biochem J 1996 Feb 15;314 ( Pt 1)(Pt 1):139-44.
- Cheesman MR, le Brun NE, Kadir FH, Thomson AJ, Moore GR, Andrews SC, Guest JR, Harrison PM, Smith JM, Yewdall SJ. Haem and non-haem iron sites in Escherichia coli bacterioferritin: spectroscopic and model building studies.. Biochem J 1993 May 15;292 ( Pt 1)(Pt 1):47-56.
- Bauminger ER, Harrison PM, Hechel D, Hodson NW, Nowik I, Treffry A, Yewdall SJ. Iron (II) oxidation and early intermediates of iron-core formation in recombinant human H-chain ferritin.. Biochem J 1993 Dec 15;296 ( Pt 3)(Pt 3):709-19.
- Bauminger ER, Treffry A, Hudson AJ, Hechel D, Hodson NW, Andrews SC, Levi S, Nowik I, Arosio P, Guest JR. Iron incorporation into ferritins: evidence for the transfer of monomeric Fe(III) between ferritin molecules and for the formation of an unusual mineral in the ferritin of Escherichia coli.. Biochem J 1994 Sep 15;302 ( Pt 3)(Pt 3):813-20.
- Treffry A, Bauminger ER, Hechel D, Hodson NW, Nowik I, Yewdall SJ, Harrison PM. Defining the roles of the threefold channels in iron uptake, iron oxidation and iron-core formation in ferritin: a study aided by site-directed mutagenesis.. Biochem J 1993 Dec 15;296 ( Pt 3)(Pt 3):721-8.
- Joo MS, Tourillon G, Sayers DE, Theil EC. Rapid reduction of iron in horse spleen ferritin by thioglycolic acid measured by dispersive X-ray absorption spectroscopy.. Biol Met 1990;3(3-4):171-5.
- Levi S, Yewdall SJ, Harrison PM, Santambrogio P, Cozzi A, Rovida E, Albertini A, Arosio P. Evidence of H- and L-chains have co-operative roles in the iron-uptake mechanism of human ferritin.. Biochem J 1992 Dec 1;288 ( Pt 2)(Pt 2):591-6.
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