![]() ![]() In many bacteria, iron is stored in three types of protein, ferritin, bacterioferritin, and possibly in DNA binding protein from starved cells (Dps). Iron storage proteins enable iron homeostasis by allowing the accumulation of intracellular iron while simultaneously ameliorating the toxicity mediated by the extreme insolubility of Fe 3+ and the oxidative stress resulting from uncontrolled Fe 2+/Fe 3+ redox cycling. The requirement of iron as a nutrient, the reactivity of Fe 2+ toward O 2 and H 2O 2, and the insolubility of Fe 3+ at biologically compatible pH present significant challenges to bacterial cells, which are managed by the iron homeostasis machinery (iron uptake, storage, and utilization). Surprisingly, incubating Pa Dps and DNA revealed unprecedented DNA cleaving activity that is independent of H 2O 2 or O 2 but requires divalent cations and 12-mer Pa Dps. ![]() The Pa Dps structure harbors a novel network of Tyr residues at the interface of each subunit dimer between the two di-iron centers, which captures radicals generated during Fe 2+ oxidation at the ferroxidase centers and forms di-tyrosine linkages, thus effectively trapping the radicals within the Dps shell. aeruginosa Δ dps mutant is significantly more susceptible to H 2O 2 than the parent strain. aeruginosa to survive H 2O 2-mediated oxidative stress. In vitro, the di-iron centers catalyze the oxidation of Fe 2+ utilizing H 2O 2 (not O 2) as an oxidant, suggesting Pa Dps functions to aid P. The 12-Mer Pa Dps contains two di-iron centers at the interface of each subunit dimer, coordinated by conserved His, Glu, and Asp residues. The protein, termed Pa Dps, adopts the Dps subunit fold and oligomerizes into a nearly spherical 12-mer quaternary structure at pH 6.0 or in the presence of divalent cations at neutral pH and above. ![]() We report the structural, biochemical, and functional characterization of the product of gene PA0962 from Pseudomonas aeruginosa PAO1. ![]()
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