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A novel mechanism of iron-core formation by Pyrococcus furiosus archaeoferritin, a member of an uncharacterized branch of the ferritin-like superfamily.

Ebrahimi KH, Hagedoorn PL, van der Weel L, Verhaert PD, Hagen WR - J. Biol. Inorg. Chem. (2012)

Bottom Line: Although the function of these iron-storage proteins is constitutive to many organisms to sustain life, the genome of some organisms appears not to encode any of these proteins.Monomers catalyze oxidation of Fe(II) and they store the Fe(III) product as they assemble to form structures comparable to those of 24-meric ferritin.We propose that this mechanism is an alternative method of iron storage by the ferritin-like superfamily of proteins in organisms that lack the regular preassociated 24-meric/12-meric ferritins.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.

ABSTRACT
Storage of iron in a nontoxic and bioavailable form is essential for many forms of life. Three subfamilies of the ferritin-like superfamily, namely, ferritin, bacterioferritin, and Dps (DNA-binding proteins from starved cells), are able to store iron. Although the function of these iron-storage proteins is constitutive to many organisms to sustain life, the genome of some organisms appears not to encode any of these proteins. In an attempt to identify new iron-storage systems, we have found and characterized a new member of the ferritin-like superfamily of proteins, which unlike the multimeric storage system of ferritin, bacterioferritin, and Dps is monomeric in the absence of iron. Monomers catalyze oxidation of Fe(II) and they store the Fe(III) product as they assemble to form structures comparable to those of 24-meric ferritin. We propose that this mechanism is an alternative method of iron storage by the ferritin-like superfamily of proteins in organisms that lack the regular preassociated 24-meric/12-meric ferritins.

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Spectroscopy of Fe(III)-loaded protein. a Optical spectrum of AFR containing 20 Fe(III) ions per monomer in comparison with that of PfFtn containing 500 Fe(II) ions per 24-mer. The AFR concentration was 39.5 μM (monomer) and the PfFtn concentration was 36.5 μM (monomer). b EPR spectra of 640 μM (monomer) AFR: from top to bottom apo-AFR and AFR containing 40 Fe(III) ions per monomer. c EPR spectrum of 540 μM (monomer) PfFtn containing 50 Fe(III) ions per monomer. The EPR conditions were as follows: microwave frequency, 9.24 GHz; microwave power, 200 mW; modulation frequency, 100 kHz; modulation amplitude, 12.5 G; temperature, 110 K
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Fig6: Spectroscopy of Fe(III)-loaded protein. a Optical spectrum of AFR containing 20 Fe(III) ions per monomer in comparison with that of PfFtn containing 500 Fe(II) ions per 24-mer. The AFR concentration was 39.5 μM (monomer) and the PfFtn concentration was 36.5 μM (monomer). b EPR spectra of 640 μM (monomer) AFR: from top to bottom apo-AFR and AFR containing 40 Fe(III) ions per monomer. c EPR spectrum of 540 μM (monomer) PfFtn containing 50 Fe(III) ions per monomer. The EPR conditions were as follows: microwave frequency, 9.24 GHz; microwave power, 200 mW; modulation frequency, 100 kHz; modulation amplitude, 12.5 G; temperature, 110 K

Mentions: To verify that the AFR has the ability to store Fe(III) in a manner similar to that of ferritin, apo-AFR was aerobically incubated with an amount of ferrous iron corresponding to a stoichiometry of 20 Fe(II) ions per monomer for 3 h at room temperature and subsequently the UV–vis spectrum of the sample was measured between 300 and 800 nm and compared with the spectrum of PfFtn aerobically loaded with the same amount of Fe(II) per monomer, as shown in Fig. 6a. The spectrum of the loaded AFR is very similar to that of Fe(III)-loaded PfFtn, and thus suggests that a ferrihydrite-like mineral core was formed. The molar extinction coefficient of 2.4 ± 0.2 mM−1 cm−1 at 315 nm for the putative AFR core is close to the reported values for the core of PfFtn (2.5 mM−1 cm−1 at 315 nm) [25] and human H-chain ferritin (2.1 mM−1 cm−1 at 305 nm) [33].Fig. 6


A novel mechanism of iron-core formation by Pyrococcus furiosus archaeoferritin, a member of an uncharacterized branch of the ferritin-like superfamily.

Ebrahimi KH, Hagedoorn PL, van der Weel L, Verhaert PD, Hagen WR - J. Biol. Inorg. Chem. (2012)

Spectroscopy of Fe(III)-loaded protein. a Optical spectrum of AFR containing 20 Fe(III) ions per monomer in comparison with that of PfFtn containing 500 Fe(II) ions per 24-mer. The AFR concentration was 39.5 μM (monomer) and the PfFtn concentration was 36.5 μM (monomer). b EPR spectra of 640 μM (monomer) AFR: from top to bottom apo-AFR and AFR containing 40 Fe(III) ions per monomer. c EPR spectrum of 540 μM (monomer) PfFtn containing 50 Fe(III) ions per monomer. The EPR conditions were as follows: microwave frequency, 9.24 GHz; microwave power, 200 mW; modulation frequency, 100 kHz; modulation amplitude, 12.5 G; temperature, 110 K
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3401498&req=5

Fig6: Spectroscopy of Fe(III)-loaded protein. a Optical spectrum of AFR containing 20 Fe(III) ions per monomer in comparison with that of PfFtn containing 500 Fe(II) ions per 24-mer. The AFR concentration was 39.5 μM (monomer) and the PfFtn concentration was 36.5 μM (monomer). b EPR spectra of 640 μM (monomer) AFR: from top to bottom apo-AFR and AFR containing 40 Fe(III) ions per monomer. c EPR spectrum of 540 μM (monomer) PfFtn containing 50 Fe(III) ions per monomer. The EPR conditions were as follows: microwave frequency, 9.24 GHz; microwave power, 200 mW; modulation frequency, 100 kHz; modulation amplitude, 12.5 G; temperature, 110 K
Mentions: To verify that the AFR has the ability to store Fe(III) in a manner similar to that of ferritin, apo-AFR was aerobically incubated with an amount of ferrous iron corresponding to a stoichiometry of 20 Fe(II) ions per monomer for 3 h at room temperature and subsequently the UV–vis spectrum of the sample was measured between 300 and 800 nm and compared with the spectrum of PfFtn aerobically loaded with the same amount of Fe(II) per monomer, as shown in Fig. 6a. The spectrum of the loaded AFR is very similar to that of Fe(III)-loaded PfFtn, and thus suggests that a ferrihydrite-like mineral core was formed. The molar extinction coefficient of 2.4 ± 0.2 mM−1 cm−1 at 315 nm for the putative AFR core is close to the reported values for the core of PfFtn (2.5 mM−1 cm−1 at 315 nm) [25] and human H-chain ferritin (2.1 mM−1 cm−1 at 305 nm) [33].Fig. 6

Bottom Line: Although the function of these iron-storage proteins is constitutive to many organisms to sustain life, the genome of some organisms appears not to encode any of these proteins.Monomers catalyze oxidation of Fe(II) and they store the Fe(III) product as they assemble to form structures comparable to those of 24-meric ferritin.We propose that this mechanism is an alternative method of iron storage by the ferritin-like superfamily of proteins in organisms that lack the regular preassociated 24-meric/12-meric ferritins.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology, Delft University of Technology, Delft, The Netherlands.

ABSTRACT
Storage of iron in a nontoxic and bioavailable form is essential for many forms of life. Three subfamilies of the ferritin-like superfamily, namely, ferritin, bacterioferritin, and Dps (DNA-binding proteins from starved cells), are able to store iron. Although the function of these iron-storage proteins is constitutive to many organisms to sustain life, the genome of some organisms appears not to encode any of these proteins. In an attempt to identify new iron-storage systems, we have found and characterized a new member of the ferritin-like superfamily of proteins, which unlike the multimeric storage system of ferritin, bacterioferritin, and Dps is monomeric in the absence of iron. Monomers catalyze oxidation of Fe(II) and they store the Fe(III) product as they assemble to form structures comparable to those of 24-meric ferritin. We propose that this mechanism is an alternative method of iron storage by the ferritin-like superfamily of proteins in organisms that lack the regular preassociated 24-meric/12-meric ferritins.

Show MeSH
Related in: MedlinePlus