Doctor of Philosophy (PhD)


Department of Chemistry

Document Type



In the P. aeruginosa genome, gene PA0962 codes for a probable DNA-binding protein from starved cells (Pa Dps). Pa Dps is assembled from 12 monomers, each consisting of a four-helix bundle fold typical of Dps proteins. A subunit dimer of Pa Dps harbors two ferroxidase centers. Assembly of a dodecameric structure of Pa Dps is favored by the presence of divalent metal ions and at pH 6.0 in the absence or presence of divalent cations. Pa Dps is unable to form the large DNA-protein complexes typical of many Dps proteins. Instead, Pa Dps acts on plasmid DNA to form relaxed (nicked) and linearized DNA. Increasing the protein-to-DNA mole ratio results in smears and small DNA fragments in agarose gel electrophoresis. The nuclease activity of 12-mer Pa Dps is enhanced in the presence of divalent cations and low ionic strength. Pa Dps ferroxidase centers can oxidize Fe2+ ions using H2O2 as an oxidant and form a Fe3+ iron mineral core. The Pa Dps X-ray crystal structure revealed a unique network of 10 tyrosine residues at the subunit dimer interface, halfway between the two ferroxidase centers. Pa Dps uses this tyrosine network to trap hydroxyl radicals leaking from the ferroxidase center during Fe2+oxidation, thus protecting the P. aeruginosa cells from H2O2-mediated oxidative stress.

The gene PA4880 in the P. aeruginosa genome codes for a Dps-like protein (Pa DpsL). It is a dodecameric, nearly spherical shell-like structure that shares common structural and functional features with Pa Dps and Pa bacterioferritin. The monomer of the protein harbors a ferroxidase center, which can bind two Fe ions. The assembly of a dodecameric structure in Pa DpsL is stabilized by the presence of divalent cations. Both 6-mer and 12-mer oligomeric assemblies of Pa DpsL show nuclease activity at pH 6.0–8.5. High ionic strength favors the formation of nicked DNA. Pa DpsL ferroxidase centers utilize O2 or H2O2 as the oxidant and form an Fe3+ iron mineral core. The formation of mineral cores was more efficient with O2. The contribution of Pa DpsL to combat H2O2-mediated oxidative stress in P. aeruginosa cells was not as significant as the effect of Pa Dps under the experimental conditions employed.



Committee Chair

Rivera, Mario E.

Available for download on Wednesday, October 23, 2024

Included in

Biochemistry Commons