36 research outputs found
to Penetrate into Epithelial Cells and to Induce an Inflammatory Response
No full textThe 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
Evolutionary Conservation of Zinc-Mediated Nutritional Immunity Across Vertebrates and Insects in Host-Pathogen Interactions
No full textSalmonella typhimurium and pseudomonas aeruginosa respond differently to the fe chelator deferiprone and to some novel deferiprone derivatives
No full textThe ability to obtain Fe is critical for pathogens to multiply in their host. For this reason,
there is significant interest in the identification of compounds that might interfere with Fe management in bacteria. Here we have tested the response of two Gram-negative pathogens, Salmonella
enterica serovar Typhimurium (STM) and Pseudomonas aeruginosa (PAO1), to deferiprone (DFP),
a chelating agent already in use for the treatment of thalassemia, and to some DFP derivatives
designed to increase its lipophilicity. Our results indicate that DFP effectively inhibits the growth of
PAO1, but not STM. Similarly, Fe-dependent genes of the two microorganisms respond differently to
this agent. DFP is, however, capable of inhibiting an STM strain unable to synthesize enterochelin,
while its effect on PAO1 is not related to the capability to produce siderophores. Using a fluorescent
derivative of DFP we have shown that this chelator can penetrate very quickly into PAO1, but not
into STM, suggesting that a selective receptor exists in Pseudomonas. Some of the tested derivatives
have shown a greater ability to interfere with Fe homeostasis in STM compared to DFP, whereas
most, although not all, were less active than DFP against PAO1, possibly due to interference of the
added chemical tails with the receptor-mediated recognition process. The results reported in this
work indicate that DFP can have different effects on distinct microorganisms, but that it is possible to
obtain derivatives with a broader antimicrobial actio
Carbon monoxide binding to the heme group at the dimeric interface modulates structure and copper accessibility in the Cu,Zn superoxide dismutase from Haemophilus ducreyi: In silico and in vitro evidences
No full textX-ray absorption near-edge structure (XANES) spectroscopy and molecular dynamics (MD) simulations have been jointly applied to the study of the Cu,Zn superoxide dismutase from Haemophilus ducreyi (HdSOD) in interaction with the carbon monoxide molecule. The configurational flexibility of the Fe(II)-heme group, intercalated between the two subunits, has been sampled by MD simulations and included in the XANES data analysis without optimization in the structural parameter space. Our results provide an interpretation of the observed discrepancy in the Fe-heme distances as detected by extended X-ray absorption fine structure (EXAFS) spectroscopy and the classical XANES analysis, in which the structural parameters are optimized in a unique structure. Moreover, binding of the CO molecule to the heme induces a long range effect on the Cu,Zn active site, as evidenced by both MD simulations and in vitro experiments. MD simulation of the CO bound system, in fact, highlighted a structural rearrangement of the protein-protein hydrogen bond network in the region of the Cu,Zn active site, correlated with an increase in water accessibility at short distance from the copper atom. In line, in vitro experiments evidenced an increase of copper accessibility to a chelating agent when the CO molecule binds to the heme group, as compared to a heme deprived HdSOD. Altogether, our results support the hypothesis that the HdSOD is a heme-sensor protein, in which binding to small gaseous molecules modulates the enzyme superoxide activity as an adaptive response to the bacterial environment. Copyright © 2012 Taylor & Francis
G. mellonella is a suitable model for studying P. aeruginosa response to the host nutritional immunity strategies
No full textStructural Basis of Heme Binding in the Cu,Zn Superoxide Dismutase from Haemophilus ducreyi
No full textThe Cu,Zn superoxide dismutase from Haemophilus ducreyi is characterized by the unique ability to bind heme at its dimer interface. Here we report the high-resolution crystal structures of this protein in the heme-loaded (holo) and heme-free (apo) forms. Heme is asymmetrically bound between the two enzyme subunits, where heme iron is coordinated by two histidine residues, His64 and His 124, provided by the two subunits. Moreover, the binding of heme to the protein is ensured by stabilizing contacts between the prosthetic group and a limited number of other residues, most of which are not present in other bacterial enzyme variants. We show that the introduction of only three mutations at the dimer interface of the enzyme from Haemophilus parainfluenzae, a closely related bacterial species, is sufficient to induce heme-binding ability by this enzyme variant. Heme binding does not alter protein activity. Moreover, the binding of the prosthetic group does not induce any significant structural perturbation at the subunit level and requires only limited local structural rearrangements that widen the cleft at the dimer interface and cause a limited shift in the relative orientation between the subunits. The presence of a preformed heme-binding pocket and the significant solvent exposure of the cofactor to the solvent are compatible with the suggested protective role of the enzyme against hen-le toxicity or with its involvement in heme trafficking in the periplasmic space. (C) 2008 Elsevier Ltd. All rights reserved
Studio delle proprieta molecolari e funzionali delle Cu,-ZnSOD nei batteri gram negativi
No full textDottorato di ricerca in scienze biochimiche e biomolecolari. 12. ciclo.Consiglio Nazionale delle Ricerche Biblioteca Centrale P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale Piazza Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
Pseudomonas aeruginosa transcriptional reprogramming during zinc starvation reveals a shift toward anaerobic respiration
No full textZinc-binding metallophores protect Pseudomonas aeruginosa from calprotectin-mediated metal starvation
No full textThe ability to produce a metallophore that can extract the metal from zinc-binding proteins contributes to the remarkable ability of Pseudomona aeruginosa to proliferate in zinc-poor environments.Pseudomonas aeruginosa is known to exhibit considerable resistance to the antimicrobial activity of the metal-sequestering protein calprotectin (CP). In this study, we demonstrate that although CP induces zinc deficiency in P. aeruginosa, a strain unable to import zinc through the two most important metal acquisition systems, namely ZnuABC and ZrmABCD, maintains significant growth capacity in the presence of high concentrations of CP. Furthermore, we have shown that nicotianamine, a molecule structurally similar to the metallophore pseudopaline, can favor the acquisition of the metal even in the presence of CP. To gain insights into the mechanisms through which metallophores can promote zinc acquisition, we analyzed the effect of nicotianamine on the activity of the metallo-beta-lactamase VIM-1. Our data suggest that metallophores released by bacteria in response to zinc deficiency can extract the protein-bound metal. The ability to interfere with the binding of metals to proteins, as well as favoring the acquisition of zinc, may contribute to increasing the resistance of P. aeruginosa to the antimicrobial action of CP
Localized Infections with P. aeruginosa Strains Defective in Zinc Uptake Reveal That Zebrafish Embryos Recapitulate Nutritional Immunity Responses of Higher Eukaryotes
No full textThe innate immune responses of mammals to microbial infections include strategies based on manipulating the local concentration of metals such as iron (Fe) and zinc (Zn), commonly described as nutritional immunity. To evaluate whether these strategies are also present in zebrafish embryos, we have conducted a series of heart cavity-localized infection experiments with Pseudomonas aeruginosa strains characterized by a different ability to acquire Zn. We have found that, 48 h after infection, the bacterial strains lacking critical components of the Zn importers ZnuABC and ZrmABCD have a reduced colonization capacity compared to the wild-type strain. This observation, together with the finding of a high level of expression of Zur-regulated genes, suggests the existence of antimicrobial mechanisms based on Zn sequestration. However, we have observed that strains lacking such Zn importers have a selective advantage over the wild-type strain in the early stages of infection. Analysis of the expression of the gene that encodes for a Zn efflux pump has revealed that at short times after infection, P. aeruginosa is exposed to high concentrations of Zn. At the same time, zebrafish respond to the infection by activating the expression of the Zn transporters Slc30a1 and Slc30a4, whose mammalian homologs mediate a redistribution of Zn in phagocytes aimed at intoxicating bacteria with a metal excess. These observations indicate that teleosts share similar nutritional immunity mechanisms with higher vertebrates, and confirm the usefulness of the zebrafish model for studying host–pathogen interactions
