The ferritin-like domain is an about 145-residue domain made of a four-helix bundle surrounding a non-heme, non-sulfur, oxo-bridged diiron site (see <PDB:1RYT>). The diiron site is contained within a twisted, left-handed four-helix-bundle constituted of two anti-parallel helix pairs connected through a left-handed crossover connection. Known ligand residues at non-heme, non-sulfur diiron sites in proteins include His, Asp, Glu, and Tyr. Proteins containing a ferritin-like diiron domain possess the ability to catalyze oxidation of Fe(2+) to Fe(3+) by O2, i.e. ferroxidase activity. The ferritin-like diiron domain occurs in stand-alone form in ferritin and bacterioferritin or in association with the rubredoxin-like domain (see <PDOC50903>) in rubrerythrin [1,2,3].

Proteins known to contain a ferritin-like diiron domain are listed below:

• Ferritin (Ftn), an eukaryotic intracellular protein that stores iron in a soluble, nontoxic, readily available form (see <PDOC00181>).
• Bacterioferritin (Bfr), a prokaryotic protein which may perform functions in iron detoxification and storage.
• Rubrerythrin (Rr), a non-heme protein isolated from anaerobic sulfate- reducing bacteria.
• Nigerythrin (Nr), a prokaryotic protein of unknown function.

The profile we developed covers the entire ferritin-like diiron domain.