Family

Bacterioferritin (IPR002024)

Short name: Bacterioferritin

Family relationships

None.

Description

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.
PRINTS
PROSITE patterns
PIRSF
TIGRFAMs
CDD