<p>This entry represents a group of proteins, containing ferritin-like domain, which is an about 145-residue domain made of a four-helixbundle surrounding a non-heme, non-sulphur, oxo-bridged diiron site. The diiron site is contained within a twisted, left-handed four-helix-bundle constituted of two anti-parallel helix pairs connected through aleft-handed crossover connection. Known ligand residues at non-heme, non-sulphur diiron sites in proteins include His, Asp, Glu, and Tyr. Proteinscontaining a ferritin-like diiron domain possess the ability to catalyzeoxidation of Fe²⁺ to Fe²⁺ by O₂, i.e. ferroxidase activity. The ferritin-like diiron domain occurs in stand-alone form in ferritin and bacterioferritinor in association with the rubredoxin-like domain inrubrerythrin [<cite idref="PUB00008767"/>].Proteins known to contain a ferritin-like diiron domain are listed below: </p><li> Ferritin (Ftn), an eukaryotic intracellular protein that stores iron in a soluble, nontoxic, readily available form.</li><li>Bacterioferritin (Bfr), a prokaryotic protein which may perform functions in iron detoxification and storage.</li><li>Rubrerythrin (Rr), a non-heme protein isolated from anaerobic sulphate- reducing bacteria.</li><li>Nigerythrin (Nr), a prokaryotic protein of unknown function.</li> Ferritin-like