DNA-Binding Proteins From Starved Cells (Dps Proteins)

In the recent past over 200 Dps (DNA-binding proteins from starved cells) proteins have been identified in bacterial genomes. Dps proteins belong to the ferritin superfamily. They are expressed under conditions of oxidative and/or nutritional stress and are characterized by a highly conserved shell-like structure of 12 identical subunits assembled with 23 symmetry. The internal cavity is designed to accommodate up to 500 iron/atoms per molecule in a soluble and bioavailable form. Dps proteins play an important role in the complex protection mechanism against oxidative damage. The presence of a highly conserved ferroxidase center, which uses hydrogen peroxide as physiological iron oxidant, confers to all Dps proteins the capacity to decrease the production of the hydroxyl-radicals and, hence, to prevent the damage to DNA and other cellular components. Ferroxidase activity is of special importance in pathogenic bacteria since production of hydrogen peroxide in macrophages and neutrophiles represents one of the first host defense mechanisms. The capacity to bind DNA in a nonspecific manner and pack it into condensed structures, an attribute limited to some members of the family, represents the second distinctive mechanism used to advantage by Dps proteins for the survival of the organism.