Structural basis for iron mineralization by bacterioferritin

Crow, Allister, Lawson, Tamara L., Lewin, Allison, Moore, Geoff and Le Brun, Nick ORCID: (2009) Structural basis for iron mineralization by bacterioferritin. Journal of the American Chemical Society, 131 (19). pp. 6808-6813.

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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: Article
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Biophysical Chemistry (former - to 2017)
Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Faculty of Science > Research Centres > Centre for Molecular and Structural Biochemistry
Faculty of Science > Research Groups > Chemistry of Life Processes
Depositing User: Rachel Smith
Date Deposited: 23 Mar 2011 10:38
Last Modified: 16 Jan 2024 01:21
DOI: 10.1021/ja8093444

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