Pseudomonas Aeruginosa Dps

Abstract

Abstract DNA‐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 Fe 2+ by consuming H 2 O 2 and storing the resultant Fe 3+ in the interior cavity, thus simultaneously defending against Fe 2+ ‐ and H 2 O 2 ‐mediated oxidative stress and compartmentalizing the otherwise insoluble Fe 3+ . 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 from Pseudomonas 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 Fe 2+ to Fe 3+ using H 2 O 2 as an electron acceptor, and the protein stores the ensuing Fe 3+ in its interior cavity, therefore, enabling P. aeruginosa cells to survive challenges with H 2 O 2 . 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 Fe 2+ at ferroxidase centers; and (ii) endonuclease activity (phosphodiester hydrolysis) which depends on an intact 12‐mer quaternary structure in solution.