The So-Called Listeria innocua Ferritin Is a Dps Protein. Iron Incorporation, Detoxification, and DNA Protection Properties
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- 作者：Meihong Su ; Stefano Cavallo ; Simonetta Stefanini ; Emilia Chiancone ; and N. Dennis Chasteen
- 刊名：Biochemistry
- 出版年：2005
- 出版时间：April 19, 2005
- 年：2005
- 卷：44
- 期：15
- 页码：5572 - 5578
- 全文大小：166K
- 年卷期：v.44,no.15(April 19, 2005)
- ISSN：1520-4995
文摘
Listeria innocua Dps (DNA binding protein from starved cells) affords protection to DNAagainst oxidative damage and can accumulate about 500 iron atoms within its central cavity through aprocess facilitated by a ferroxidase center. The chemistry of iron binding and oxidation in Listeria Dps(LiDps, formerly described as a ferritin) using H2O2 as oxidant was studied to further define the mechanismof iron deposition inside the protein and the role of LiDps in protecting DNA from oxidative damage.The relatively strong binding of 12 Fe2+ to the apoprotein (KD ~ 0.023 
M) was demonstrated by isothermaltitration calorimetry, fluorescence quenching, and pH stat experiments. Hydrogen peroxide was found tobe a more efficient oxidant for the protein-bound Fe2+ than O2. Iron(II) oxidation by H2O2 occurs witha stoichiometry of 2 Fe2+/H2O2 in both the protein-based ferroxidation and subsequent mineralizationreactions, indicating complete reduction of H2O2 to H2O. Electron paramagnetic resonance (EPR) spin-trapping experiments demonstrated that LiDps attenuates the production of hydroxyl radical by Fentonchemistry. DNA cleavage assays showed that the protein, while not binding to DNA itself, protects itagainst the deleterious combination of Fe2+ and H2O2. The overall process of iron deposition anddetoxification by LiDps is described by the following equations. For ferroxidation, Fe2+ + DpsZ 
[(Fe2+)-Dps]Z+1 + H+ (Fe2+ binding) and [(Fe2+)-Dps]Z+1 + Fe2+ + H2O2 [(Fe3+)2(O)2-Dps]Z+1 + 2H+ (Fe2+oxidation/hydrolysis). For mineralization, 2Fe2+ + H2O2 + 2H2O 2Fe(O)OH(core) + 4H+ (Fe2+ oxidation/hydrolysis). These reactions occur in place of undesirable odd-electron redox processes that producehydroxyl radical.
M) was demonstrated by isothermaltitration calorimetry, fluorescence quenching, and pH stat experiments. Hydrogen peroxide was found tobe a more efficient oxidant for the protein-bound Fe2+ than O2. Iron(II) oxidation by H2O2 occurs witha stoichiometry of 2 Fe2+/H2O2 in both the protein-based ferroxidation and subsequent mineralizationreactions, indicating complete reduction of H2O2 to H2O. Electron paramagnetic resonance (EPR) spin-trapping experiments demonstrated that LiDps attenuates the production of hydroxyl radical by Fentonchemistry. DNA cleavage assays showed that the protein, while not binding to DNA itself, protects itagainst the deleterious combination of Fe2+ and H2O2. The overall process of iron deposition anddetoxification by LiDps is described by the following equations. For ferroxidation, Fe2+ + DpsZ [(Fe2+)-Dps]Z+1 + H+ (Fe2+ binding) and [(Fe2+)-Dps]Z+1 + Fe2+ + H2O2 [(Fe3+)2(O)2-Dps]Z+1 + 2H+ (Fe2+oxidation/hydrolysis). For mineralization, 2Fe2+ + H2O2 + 2H2O 2Fe(O)OH(core) + 4H+ (Fe2+ oxidation/hydrolysis). These reactions occur in place of undesirable odd-electron redox processes that producehydroxyl radical.