Pseudomonas Aeruginosa Dps

AbstractDNA‐binding proteins from starved cells (Dps) are part of the ferritin family. Unlike ferritin and bacterioferritin, which are assembled from 24 subunits, the quaternary structure of Dps is an assembly of 12 subunits that forms a nearly spherical shell enclosing a hollow interior cavity. Dps are known to oxidize Fe2+by consuming H2O2and storing the resultant Fe3+in the interior cavity, thus simultaneously defending against Fe2+‐ and H2O2‐mediated oxidative stress and compartmentalizing the otherwise insoluble Fe3+. Some Dps can bind DNA, forming stable complexes that provide a physical shield that guards DNA from various stressors. Among the numerous Dps proteins characterized so far, the Dps fromPseudomonas aeruginosa(Pa Dps) exhibits structural and functional similarities with other Dps proteins but also possesses unique attributes. The dodecameric quaternary structure of Pa Dps is stabilized at pH ≤ 6.0, and by the presence of divalent metal cations at pH ≥ 7.5. Conserved His, Glu, and Asp residues coordinate iron of the di‐nuclear (ferroxidase) centers at the interface of each subunit dimer. The ferroxidase centers in Pa Dps catalyze the oxidation of Fe2+to Fe3+using H2O2as an electron acceptor, and the protein stores the ensuing Fe3+in its interior cavity, therefore, enablingP. aeruginosacells to survive challenges with H2O2. Pa Dps exhibits two unprecedented properties: (i) the presence of a novel network of Tyr residues at the interface of each subunit dimer, between the two ferroxidase centers, which captures radicals produced during the oxidation of Fe2+at ferroxidase centers; and (ii) endonuclease activity (phosphodiester hydrolysis) which depends on an intact 12‐mer quaternary structure in solution.