Bacterioferritin (IPR002024)

Short name: Bacterioferritin

Overlapping homologous superfamilies

Family relationships



Bacterioferritin (BFR; also known as cytochrome b1 or cytochrome b557) [PMID: 2276500, PMID: 1904771] of Escherichia coli is an iron-storage protein consisting of 24 identical subunits that pack together to form a highly symmetrical, nearly spherical shell surrounding a central cavity of about 8 nm diameter [PMID: 8695634, PMID: 8526846]. X-ray crystallographic studies have revealed a close structural similarity between BFR and the ferritins, a family of iron-storage proteins found in both eukaryotes and bacteria [PMID: 8695634]. Common to both ferritins and BFRs is a capacity to store large quantities of iron within their hollow interior, in the form of a hydrated ferric oxide mineral containing variable amounts of phosphate anion. However, a major difference between them is that BFR contains up 12 b-type haem groups, while ferritins, as isolated, do not contain haem.

The building block for the BFR shell is a protein dimer (subunits A and B) binding the single haem group. Each subunit consists of four nearly parallel alpha-helices. The haem is bound symmetrically to subunits A and B by Met(A)-52 and Met(B)-52 residues [PMID: 7664064]. Each subunit includes a binuclear metal-binding site linking together the four major helices of the subunit, which has been identified as the ferroxidase centre of BFR [PMID: 8526846]. The ferroxidase centre is where that initial oxidation of ferrous iron by molecular oxygen occurs, facilitating the detoxification of iron, protection against dioxygen and radical products, and storage of ferric-hydroxyphosphate at the core [PMID: 9889981]. BFR mutants with Met-52 replaced are haem-free, but appear to be correctly assembled and are capable of accumulating iron [PMID: 7559480]. Some bacterioferritins are composed of two subunit types, one conferring heme-binding ability (alpha) and the other (beta) bestowing ferroxidase activity [PMID: 9889981].

GO terms

Biological Process

GO:0006879 cellular iron ion homeostasis
GO:0006826 iron ion transport

Molecular Function

GO:0008199 ferric iron binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns