Physical Evidence that Yeast Frataxin Is an Iron Storage Protein
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- 作者：Oleksandr Gakh ; Jiri Adamec ; A. Marquis Gacy ; Ray D. Twesten ; Whyte G. Owen ; and Grazia Isaya
- 刊名：Biochemistry
- 出版年：2002
- 出版时间：May 28, 2002
- 年：2002
- 卷：41
- 期：21
- 页码：6798 - 6804
- 全文大小：198K
- 年卷期：v.41,no.21(May 28, 2002)
- ISSN：1520-4995
文摘
Frataxin is a conserved mitochondrial protein required for iron homeostasis. We showedpreviously that in the presence of ferrous iron recombinant yeast frataxin (mYfh1p) assembles into aregular multimer of ~1.1 MDa storing ~3000 iron atoms. Here, we further demonstrate that mYfh1p andiron form a stable hydrophilic complex that can be detected by either protein or iron staining onnondenaturing polyacrylamide gels, and by either interference or absorbance measurements at sedimentationequilibrium. The molecular mass of this complex has been refined to 840 kDa corresponding to 48 proteinsubunits and 2400 iron atoms. Solution density measurements have determined a partial specific volumeof 0.58 cm3/g, consistent with the amino acid composition of mYfh1p and the presence of 50 Fe-Oequivalents per subunit. By dynamic light scattering, we show that the complex has a radius of ~11 nmand assembles within 2 min at 30 
deg.gif">C when ferrous iron, not ferric iron or other divalent cations, is addedto mYfh1p monomer at pH between 6 and 8. Iron-rich granules with diameter of 2-4 nm are detected inthe complex by scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy.These findings support the hypothesis that frataxin is an iron storage protein, which could explain themitochondrial iron accumulation and oxidative damage associated with frataxin defects in yeast, mouse,and humans.
deg.gif">C when ferrous iron, not ferric iron or other divalent cations, is addedto mYfh1p monomer at pH between 6 and 8. Iron-rich granules with diameter of 2-4 nm are detected inthe complex by scanning transmission electron microscopy and energy-dispersive X-ray spectroscopy.These findings support the hypothesis that frataxin is an iron storage protein, which could explain themitochondrial iron accumulation and oxidative damage associated with frataxin defects in yeast, mouse,and humans.