3E1M

Crystal structure of E. coli Bacterioferritin (BFR) obtained after soaking APO-BFR crystals for 2.5 minutes in FE2+ (2.5M FE(II)-BFR)

Summary for 3E1M

• Entry DOI: 10.2210/pdb3e1m/pdb
• Related: 3E1J 3E1L 3E1N 3E1O 3E1P 3E1Q
• Descriptor: BACTERIOFERRITIN, SULFATE ION, FE (II) ION, ... (5 entities in total)
• Functional Keywords: bacterioferritin. rhombic dodecahedral superstructure., heme, iron, iron storage, metal-binding, metal binding protein
• Biological source: ESCHERICHIA COLI
• Total number of polymer chains: 12
• Total formula weight: 229462.54

Authors

Crow, A.,Lawson, T.,Lewin, A.,Moore, G.R.,Le Brun, N. (deposition date: 2008-08-04, release date: 2009-05-05, Last modification date: 2024-02-21)

Primary citation

Crow, A.,Lawson, T.L.,Lewin, A.,Moore, G.R.,Le Brun, N.E.
Structural basis for iron mineralization by bacterioferritin
J.Am.Chem.Soc., 131:6808-6813, 2009

PubMed 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-Fe(2+) forms of BFR showed that the intrasubunit catalytic center, known as the ferroxidase center, is preformed, ready to accept Fe(2+) ions with little or no reorganization. Oxidation of the di-Fe(2+) center resulted in a di-Fe(3+) center, with bridging electron density consistent with a mu-oxo or hydro bridged species. The mu-oxo bridged di-Fe(3+) center appears to be stable, and there is no evidence that Fe(3+)species are transferred into the core from the ferroxidase center. Most significantly, the data also revealed a novel Fe(2+) binding site on the inner surface of the protein, lying approximately 10 A 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 Fe(2+) 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.

PubMed: 19391621
DOI: 10.1021/ja8093444

Experimental method

X-RAY DIFFRACTION (2.7 Å)