Pseudomonas aeruginosa gene PA4880 encodes a Dps-like protein with a Dps fold, bacterioferritin-type ferroxidase centers, and endonuclease activity.

We report the biochemical, structural, and functional characterization of the protein coded by gene PA4880 in the P. aeruginosa PAO1 genome. The PA4880 gene had been annotated as coding a probable bacterioferritin. Our structural work shows that the product of gene PA4880 is a protein that adopts the Dps subunit fold, which oligomerizes into a 12-mer quaternary structure. Unlike Dps, however, the ferroxidase di-iron centers and iron coordinating ligands are buried within each subunit, in a manner identical to that observed in the ferroxidase center of P. aeruginosa bacterioferritin. Since these structural characteristics correspond to Dps-like proteins, we term the protein as P. aeruginosa Dps-like, or Pa DpsL. The ferroxidase centers in Pa DpsL catalyze the oxidation of Fe2+ utilizing O2 or H2O2 as oxidant, and the resultant Fe3+ is compartmentalized in the interior cavity. Interestingly, incubating Pa DpsL with plasmid DNA results in efficient nicking of the DNA and at higher concentrations of Pa DpsL the DNA is linearized and eventually degraded. The nickase and endonuclease activities suggest that Pa DpsL, in addition to participating in the defense of P. aeruginosa cells against iron-induced toxicity, may also participate in the innate immune mechanisms consisting of restriction endonucleases and cognate methyl transferases.

Pseudomonas aeruginosa Dps (PA0962) Functions in H2O2 Mediated Oxidative Stress Defense and Exhibits In Vitro DNA Cleaving Activity.

We report the structural, biochemical, and functional characterization of the product of gene PA0962 from Pseudomonas aeruginosa PAO1. 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. 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. In vitro, the di-iron centers catalyze the oxidation of Fe2+ utilizing H2O2 (not O2) as an oxidant, suggesting Pa Dps functions to aid P. aeruginosa to survive H2O2-mediated oxidative stress. In agreement, a P. aeruginosa Δdps mutant is significantly more susceptible to H2O2 than the parent strain. 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 Fe2+ oxidation at the ferroxidase centers and forms di-tyrosine linkages, thus effectively trapping the radicals within the Dps shell. Surprisingly, incubating Pa Dps and DNA revealed unprecedented DNA cleaving activity that is independent of H2O2 or O2 but requires divalent cations and 12-mer Pa Dps.

Is being barefoot, wearing shoes and physical activity associated with knee osteoarthritis pain flares? Data from a usually barefoot Sri Lankan cohort.

AIM: To identify the association between hours of being barefoot/wearing footwear, physical activity (PA) and knee osteoarthritis pain flares (KOAF). METHODS: Persons with a diagnosis of knee osteoarthritis, who reported previous KOAF, were followed up in a 3 months long telephone-based case-crossover study. Exposures to risk factors were assessed every 10 days and whenever the participants experienced a KOAF. Conditional logistic regression examined associations of KOAF with following: hours of being barefoot/using footwear and PA performed (P < .05). RESULTS: There were 260 persons recruited, of whom 183 continued longitudinal follow up. Of them, 120 persons had at least one valid KOAF and control period. Participants were female (90%) with mean (SD) age and body mass index of 59.9 (7.0) years, 28.0 (5.0) kg/m2 respectively. Participants were barefoot for a mean duration of 12.7 hours (SD 4.6) and used footwear for 5.1 (SD 4.7) hours daily; 99% wore heel heights <2.5 cm. Duration of being barefoot, 1 and 2 days before, demonstrated reduced multivariate odds of KOAF (odds ratio [OR] = 0.85; 95% CI 0.80-0.90). Moderate PA performed 1, 2 days prior was associated with a significantly increased risk of KOAF (multivariate OR 4.29; 2.52-7.30 and OR 3.36; 2.01-5.61). Similarly, hours of using footwear 1 and 2 days before flare demonstrated increased odds of KOAF (OR 1.15; 1.07-1.23 and 1.10; 1.03-1.18). CONCLUSIONS: Increased duration of being barefoot 1 to 2 days before is associated with reduced risk of KOAF. Performing moderate PA 1 to 2 days before was associated with an increased risk of KOAF.