Abstract
Zinc and terbium, inhibitors of iron incorporation in the ferritins, have been used for many years as probes of structure-function relationships in these proteins. Isothermal titration calorimetric and kinetic measurements of Zn(II) and Tb(III) binding and inhibition of Fe(II) oxidation were used to identify and characterize thermodynamically (n, K, ΔH°, ΔS°, and ΔG°) the functionally important binding sites for these metal ions in recombinant human H-chain, L-chain, and H-chain site-directed variant ferritins. The data reveal at least two classes of binding sites for both Zn(II) and Tb(III) in human H-chain ferritin: one strong, corresponding to binding of one metal ion in each of the eight three-fold channels, and the other weak, involving binding at the ferroxidase and nucleation sites of the protein as well as at other weak unidentified binding sites. Zn(II) and Th(III) binding to recombinant L-chain ferritin showed similar stoichiometries for the strong binding sites within the channels, but fewer weaker binding sites when compared to the H-chain protein. The kinetics and binding data indicate that the binding of Zn(II) and Tb(III) in the three-fold channels, which is the main pathway of iron(II) entry in ferritin, blocks the access of most of the iron to the ferroxidase sites on the interior of the protein, accounting for the strong inhibition by these metal ions of the oxidative deposition of iron in ferritin.
| Original language | English |
|---|---|
| Pages (from-to) | 489-497 |
| Number of pages | 9 |
| Journal | Journal of Biological Inorganic Chemistry |
| Volume | 8 |
| Issue number | 4 |
| Publication status | Published - Apr 2003 |
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Keywords
- Ferritin
- Iron oxidation
- Isothermal titration calorimetry
- Terbium binding
- Zinc binding
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Biochemistry
Cite this
Defining metal ion inhibitor interactions with recombinant human H- and L-chain ferritins and site-directed variants : An isothermal titration calorimetry study. / Bou-Abdallah, Fadi; Arosio, Paolo; Levi, Sonia; Janus-Chandler, Christine; Chasteen, N. Dennis.
In: Journal of Biological Inorganic Chemistry, Vol. 8, No. 4, 04.2003, p. 489-497.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Defining metal ion inhibitor interactions with recombinant human H- and L-chain ferritins and site-directed variants
T2 - An isothermal titration calorimetry study
AU - Bou-Abdallah, Fadi
AU - Arosio, Paolo
AU - Levi, Sonia
AU - Janus-Chandler, Christine
AU - Chasteen, N. Dennis
PY - 2003/4
Y1 - 2003/4
N2 - Zinc and terbium, inhibitors of iron incorporation in the ferritins, have been used for many years as probes of structure-function relationships in these proteins. Isothermal titration calorimetric and kinetic measurements of Zn(II) and Tb(III) binding and inhibition of Fe(II) oxidation were used to identify and characterize thermodynamically (n, K, ΔH°, ΔS°, and ΔG°) the functionally important binding sites for these metal ions in recombinant human H-chain, L-chain, and H-chain site-directed variant ferritins. The data reveal at least two classes of binding sites for both Zn(II) and Tb(III) in human H-chain ferritin: one strong, corresponding to binding of one metal ion in each of the eight three-fold channels, and the other weak, involving binding at the ferroxidase and nucleation sites of the protein as well as at other weak unidentified binding sites. Zn(II) and Th(III) binding to recombinant L-chain ferritin showed similar stoichiometries for the strong binding sites within the channels, but fewer weaker binding sites when compared to the H-chain protein. The kinetics and binding data indicate that the binding of Zn(II) and Tb(III) in the three-fold channels, which is the main pathway of iron(II) entry in ferritin, blocks the access of most of the iron to the ferroxidase sites on the interior of the protein, accounting for the strong inhibition by these metal ions of the oxidative deposition of iron in ferritin.
AB - Zinc and terbium, inhibitors of iron incorporation in the ferritins, have been used for many years as probes of structure-function relationships in these proteins. Isothermal titration calorimetric and kinetic measurements of Zn(II) and Tb(III) binding and inhibition of Fe(II) oxidation were used to identify and characterize thermodynamically (n, K, ΔH°, ΔS°, and ΔG°) the functionally important binding sites for these metal ions in recombinant human H-chain, L-chain, and H-chain site-directed variant ferritins. The data reveal at least two classes of binding sites for both Zn(II) and Tb(III) in human H-chain ferritin: one strong, corresponding to binding of one metal ion in each of the eight three-fold channels, and the other weak, involving binding at the ferroxidase and nucleation sites of the protein as well as at other weak unidentified binding sites. Zn(II) and Th(III) binding to recombinant L-chain ferritin showed similar stoichiometries for the strong binding sites within the channels, but fewer weaker binding sites when compared to the H-chain protein. The kinetics and binding data indicate that the binding of Zn(II) and Tb(III) in the three-fold channels, which is the main pathway of iron(II) entry in ferritin, blocks the access of most of the iron to the ferroxidase sites on the interior of the protein, accounting for the strong inhibition by these metal ions of the oxidative deposition of iron in ferritin.
KW - Ferritin
KW - Iron oxidation
KW - Isothermal titration calorimetry
KW - Terbium binding
KW - Zinc binding
UR - http://www.scopus.com/inward/record.url?scp=0037951337&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0037951337&partnerID=8YFLogxK
M3 - Article
VL - 8
SP - 489
EP - 497
JO - Journal of Biological Inorganic Chemistry
JF - Journal of Biological Inorganic Chemistry
SN - 0949-8257
IS - 4
ER -