Stabilization of iron in a ferrous form by ferritin. A study using dispersive and conventional x-ray absorption spectroscopy |
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Authors: | J S Rohrer M S Joo E Dartyge D E Sayers A Fontaine E C Theil |
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Institution: | Department of Biochemistry, North Carolina State University, Raleigh 27695. |
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Abstract: | Stabilization of iron in a bioavailable form is the function of ferritin, a protein of 24 subunits forming a coat around a core of less than or equal to 4500 hydrated iron atoms. The core of ferritin isolated from tissues contains Fe3+, but Fe2+ is required for experimental core formation in protein coats; reduction of Fe3+ to Fe2+ facilitates iron removal from protein coats. Using the differences in x-ray absorption spectra (x-ray absorption near edge structure) between Fe2+ and Fe3+ to monitor reconstitution of ferritin from Fe2+ and protein coats, we observed stabilization of Fe2+, apparently inside the coat. Mixtures of Fe2+ and Fe3+ persisted for greater than or equal to 16 h in air indicating that, in vivo, some iron in ferritin could be stored as Fe2+ and with Fe3+ could yield magnetite. |
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