1,720,990 research outputs found
An ERp57-mediated disulphide exchange promotes the interaction between Burkholderia cenocepacia and epithelial respiratory cells
Full text linkPrevious studies have demonstrated that extracellular glutathione reduces the ability of the Cystic Fibrosis pathogen Burkholderia cenocepacia to infect primary or immortalized epithelial respiratory cells. We report here that the adhesion and invasion ability of B. cenocepacia is limited also by thiol-oxidizing and disulphide-reducing agents and by protein disulfide isomerase (PDI) inhibitors. PDI inhibitors also reduce the proinflammatory response elicited by cells in response to Burkholderia. These findings indicate that a membrane-associated PDI catalyzes thiol/disulphide exchange reactions which favor bacterial infection. The combined use of selective PDI inhibitors, RNA silencing and specific antibodies identified ERp57 as a major PDI involved in the interaction between B. cenocepacia and epithelial cells. This study contributes to the elucidation of the Burkholderia pathogenic mechanisms by showing that this microorganism exploits a membrane-associated host protein to infect epithelial cells and identifies ERp57 as a putative pharmacological target for the treatment of Burkholderia lung infections
Low-Shear Modeled Microgravity Enhances Salmonella Enterica Resistance to Hydrogen Peroxide Through a Mechanism Involving KatG and KatN
Full text linkStudies carried out in recent years have established that growth under conditions of reduced gravity enhances Salmonella enterica serovar Typhimurium virulence. To analyze the possibility that this microgravity-induced increase in pathogenicity could involve alterations in the ability of Salmonella to withstand oxidative stress, we have compared the resistance to hydrogen peroxide of various Salmonella enterica strains grown under conditions of low shear modeled microgravity (LSMMG) or normal gravity (NG). We have found that growth in LSMMG significantly enhances hydrogen peroxide resistance of all the strains analyzed. This effect is abolished by deletion of the genes encoding for the catalases KatG and KatN, whose activity is markedly modulated by growth in LSMMG. In addition, we have observed that Salmonella enterica serovar Typhimurium strains lacking Hfq, RpoE, RpoS or OxyR are still more resistant to oxidative stress when grown in LSMMG than in NG conditions, indicating that these global gene regulators are not responsible for the microgravity-induced changes in KatG and KatN activity. As Salmonella likely encounters low shear conditions in the intestinal tract, our observations suggest that alterations in the relative activity of KatG and KatN could enhance Salmonella resistance to the reactive oxygen species produced also during natural infections
to Penetrate into Epithelial Cells and to Induce an Inflammatory Response
Full text linkThe airway surface liquid (ASL) of Cystic Fibrosis (CF) patients contains a lower concentration of reduced glutathione (GSH) with respect to healthy people. It is not known whether this defect may favor lung colonization by opportunistic pathogens. infection. and epithelial respiratory cells and inhibits the bacterial invasion into these cells. This suggests that therapies aimed at restoring normal levels of GSH in the ASL might be beneficial to control CF lung infections
X-ray Absorption Studies on the N-terminal Copper-binding Region of Haemophilus ducreyi Cu, Zn Superoxide Dismutase
No full textCopper and zinc binding properties of the N-terminal histidine-rich sequence of Haemophilus ducreyi Cu,Zn superoxide dismutase
No full textThe Cu,Zn superoxide dismutase (Cu,ZnSOD) isolated from Haemophilus ducreyi possesses a His-rich N-terminal metal binding domain, which has been previously proposed to play a copper(II) chaperoning role. To analyze the metal binding ability and selectivity of the histidine-rich domain we have carried out thermodynamic and solution structural analysis of the copper(II) and zinc(II) complexes of a peptide corresponding to the first 11 amino acids of the enzyme (H(2)N-HGDHMHNHDTK-OH, L). This peptide has highly versatile metal binding ability and provides one and three high affinity binding sites for zinc(II) and copper(II), respectively. In equimolar solutions the MHL complexes are dominant in the neutral pH-range with protonated lysine epsilon-amino group. As a consequence of its multidentate nature, L binds zinc and copper with extraordinary high affinity (K(D,Zn)=1.6x10(-9)M and K(D,Cu)=5.0x10(-12)M at pH 7.4) and appears as the strongest zinc(II) and copper(II) chelator between the His-rich peptides so far investigated. These K(D) values support the already proposed role of the N-terminal His-rich region of H. ducreyi Cu,ZnSOD in copper recruitment under metal starvation, and indicate a similar function in the zinc(II) uptake, too. The kinetics of copper(II) transfer from L to the active site of Cu-free N-deleted H. ducreyi Cu,ZnSOD showed significant pH and copper-to-peptide ratio dependence, indicating specific structural requirements during the metal ion transfer to the active site. Interestingly, the complex CuHL has significant superoxide dismutase like activity, which may suggest multifunctional role of the copper(II)-bound N-terminal His-rich domain of H. ducreyi Cu,ZnSOD
Periplasmic Cu,Zn superoxide dismutase and cytoplasmic Dps concur in protecting Salmonella enterica serovar Typhimurium from extracellular reactive oxygen species
No full textSeveral bacteria possess periplasmic Cu,Zn superoxide dismutases which can confer protection from extracellular reactive oxygen species. Thus, deletion of the sodC1 gene reduces Salmonella enterica serovar Typhimurium ability to colonize the spleens of wild type mice, but enhances virulence in p47phox mutant mice. To look into the role of periplamic Cu,Zn superoxide dismutase and into possible additive effects of the ferritin-like Dps protein involved in hydrogen peroxide detoxification, we have analyzed bacterial survival in response to extracellular sources of superoxide and/or hydrogen peroxide. Exposure to extracellular superoxide of Salmonella Typhimurium mutant strains lacking the sodC1 and sodC2 genes and/or the dps gene does not cause direct killing of bacteria, indicating that extracellular superoxide is poorly bactericidal. In contrast, all mutant strains display a sharp hydrogen peroxide-dependent loss of viability, the dps,sodC1,sodC2 mutant being less resistant than the dps or the sodC1,sodC2 mutants. These findings suggest that the role of Cu,Zn superoxide dismutase in bacteria is to remove rapidly superoxide from the periplasm to prevent its reaction with other reactive molecules. Moreover, the nearly additive effect of the sodC and dps mutations suggests that localization of antioxidant enzymes in different cellular compartments is required for bacterial resistance to extracytoplasmic oxidative attack. (C) 2007 Elsevier B.V. All rights reserved
E-HEME STRUCTURE IN CU,ZN SUPEROXIDE DISMUTASE FROM HAEMOPHILUS DUCREYI BY X-RAY ABSORPTION SPECTROSCOPY. ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
No full textDistinctive functional features in prokaryotic and eukaryotic Cu,Zn superoxide dismutases
No full textBacterial and eukaryotic Cu,Zn superoxide dismutases show remarkable differences in the active site region and in their quaternary structure organization. We report here a functional comparison between four Cu,Zn superoxide dismutases from Gram-negative bacteria and the eukaryotic bovine enzyme. Our data indicate that bacterial dimeric variants are characterized by catalytic rates higher than that of the bovine enzyme, probably due to the solvent accessibility of their active site. Prokaryotic Cu,Zn superoxide dismutases also show higher resistance to hydrogen peroxide inactivation and lower HCO3- -dependent peroxidative activity. Moreover, unlike the eukaryotic enzyme, all bacterial variants are susceptible to inactivation by chelating agents and show variable sensitivity to proteolytic attack, with the E. coli monomeric enzyme showing higher rates of inactivation by EDTA and proteinase K. We suggest that differences between individual bacterial variants could be due to the influence of modifications at the dimer interface on the enzyme conformational flexibility
Cobalt mitigates zinc-starvation effects in Pseudomonas aeruginosa
Full text linkBacterial pathogens must rapidly adapt to fluctuating metal availability within the host, where essential micronutrients are actively sequestered as part of nutritional immunity. Among these, zinc is a critical cofactor for a wide array of enzymes and regulatory proteins, and its availability is tightly linked to the expression of key virulence traits in Pseudomonas aeruginosa. This opportunistic pathogen employs different zinc acquisition systems transcriptionally regulated by the Zinc Uptake Regulator Zur, enabling its persistence within the host. Recently, Zur-controlled operons involved in the uptake/export of cobalt have been identified. Although cobalt is primarily associated with cobalamin-dependent reactions, its selective import under zinc-limiting conditions suggests a potential role for cobalt in bacterial adaptation to zinc scarcity. Yet, the functional relevance of this metal-based compensation remains poorly defined. This study shows that cobalt supplementation alleviates key effects of severe zinc deficiency in P. aeruginosa, including reduced pyocyanin production, impaired swarming motility, and enhanced sensitivity to oxidative stress. Furthermore, in vitro assays demonstrate that cobalt can functionally replace zinc in the proteases LasA and LasB and the transcriptional regulator Zur. Finally, we found that a P. aeruginosa strain deficient in the pyochelin-cobalt receptor PA2911 exhibits impaired colonization of Galleria mellonella larvae, supporting the hypothesis that cobalt compensatory function may be crucial during infection. Our results suggest that cobalt may play a broader biological role than previously recognized, highlighting its potential to support P. aeruginosa survival and pathogenicity in zinc-limiting environments
- …
