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Structural basis for iron mineralization by bacterioferritin
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Crow, Allister, Lawson, Tamara L., Lewin, Allison, Moore, Geoffrey R. and Le Brun, Nick E. (2009) Structural basis for iron mineralization by bacterioferritin. Journal of the American Chemical Society, 131 (19). pp. 6808-6813. doi:10.1021/ja8093444 ISSN 0002-7863.
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Official URL: http://dx.doi.org/10.1021/ja8093444
Abstract
Ferritin proteins function to detoxify, solubilize and store cellular iron by directing the synthesis of a ferric oxyhydroxide mineral solubilized within the protein’s central cavity. Here, through the application of X-ray crystallographic and kinetic methods, we report significant new insight into the mechanism of mineralization in a bacterioferritin (BFR). The structures of nonheme iron-free and di-Fe2+ forms of BFR showed that the intrasubunit catalytic center, known as the ferroxidase center, is preformed, ready to accept Fe2+ ions with little or no reorganization. Oxidation of the di-Fe2+ center resulted in a di-Fe3+ center, with bridging electron density consistent with a μ-oxo or hydro bridged species. The μ-oxo bridged di-Fe3+ center appears to be stable, and there is no evidence that Fe3+species are transferred into the core from the ferroxidase center. Most significantly, the data also revealed a novel Fe2+ binding site on the inner surface of the protein, lying ∼10 Å directly below the ferroxidase center, coordinated by only two residues, His46 and Asp50. Kinetic studies of variants containing substitutions of these residues showed that the site is functionally important. In combination, the data support a model in which the ferroxidase center functions as a true catalytic cofactor, rather than as a pore for the transfer of iron into the central cavity, as found for eukaryotic ferritins. The inner surface iron site appears to be important for the transfer of electrons, derived from Fe2+ oxidation in the cavity, to the ferroxidase center. Bacterioferritin may represent an evolutionary link between ferritins and class II di-iron proteins not involved in iron metabolism.
Item Type: | Journal Article | ||||||
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Divisions: | Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- ) | ||||||
Journal or Publication Title: | Journal of the American Chemical Society | ||||||
Publisher: | American Chemical Society | ||||||
ISSN: | 0002-7863 | ||||||
Official Date: | 2009 | ||||||
Dates: |
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Volume: | 131 | ||||||
Number: | 19 | ||||||
Page Range: | pp. 6808-6813 | ||||||
DOI: | 10.1021/ja8093444 | ||||||
Status: | Peer Reviewed | ||||||
Publication Status: | Published | ||||||
Access rights to Published version: | Restricted or Subscription Access |
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