DPS (DNA Protecting protein under Starved conditions) domain is a member of a broad superfamily of ferritin-like diiron-carboxylate proteins. Some DPS proteins nonspecifically bind DNA, protecting it from cleavage caused by reactive oxygen species such as the hydroxyl radicals produced during oxidation of Fe(II) by hydrogen peroxide. These proteins assemble into dodecameric structures, some form DPS-DNA co-crystalline complexes, and possess iron and H2O2 detoxification capabilities. Expression of DPS is induced by oxidative or nutritional stress, including metal ion starvation. Members of the DPS family are homopolymers formed by 12 four-helix bundle subunits that assemble with 23 symmetry into a hollow shell. The DPS ferroxidase site is unusual in that it is not located in a four-helix bundle as in ferritin, but is shared by 2-fold symmetry-related subunits providing the iron ligands. Many DPS sequences (e.g., E. coli) display an N-terminal extension of variable length that contains two or three positively charged lysine residues that extends into the solvent and is thought to play an important role in the stabilization of the complex with DNA. DPS Listeria Flp, Bacillus anthracis Dlp-1 and Dlp-2, and Helicobacter pylori HP-NAP which lack the N-terminal extension, do not bind DNA. DPS proteins from Helicobacter pylori, Treponema pallidum, and Borrelia burgdorferi are highly immunogenic.