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Haemolytic Activity (haemolytic + activity)
Selected AbstractsParallel and antiparallel dimers of magainin 2: their interaction with phospholipid membrane and antibacterial activityJOURNAL OF PEPTIDE SCIENCE, Issue 10 2002Yasuhiro Mukai Abstract Magainin 2 (M2) forms pores by associating with several other M2 molecules in lipid membranes and shows antibacterial activity. To examine the effect of M2 dimerization on biological activity and membrane interaction, parallel and antiparallel M2 dimers were prepared from two monomeric precursors. Antibacterial and haemolytic activities were enhanced by dimerization. CD measurements showed that both dimers and monomers have an ,-helical structure in the presence of lipid vesicles. Tryptophan fluorescence shift and KI quenching studies showed that all the peptides were more deeply embedded in acidic liposomes than in neutral liposomes. Experiments on dye-leakage activity and membrane translocation of peptides suggest that dimers and monomers form pores through lipid membranes, although the pore formation may be accompanied by membrane disturbance. Although dimerization of M2 increased the interaction activity with lipid membranes, no appreciable difference between the activities of parallel and antiparallel M2 dimers was observed. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source] Crystallization and preliminary crystallographic analysis of a novel haemolytic lectin from the mushroom Laetiporus sulphureusACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2004José M. Mancheño The novel haemolytic lectin from the parasitic mushroom Laetiporus sulphureus (LSL) is a homotetramer (,140,kDa) composed of subunits associated by non-covalent bonds. It exhibits haemagglutination and haemolytic activities, both of which are inhibited by N -acetyllactosamine. The structural similarity found between LSL and the bacterial pore-forming toxins mosquitocidal toxin (MTX2) from Bacillus sphaericus and ,-toxin from Clostridium septicum points to a mechanism of biological action involving the formation of pores in the target membranes. LSL has been crystallized using the hanging-drop vapour-diffusion method at 291,K. Diffraction-quality hexagonal crystals have unit-cell parameters a = b = 101.8, c = 193.9,Å and belong to space group P6322. A 2.7,Å native data set was collected with an Rmerge of 9.2%. [source] Ginsenoside Re and Notoginsenoside R1: Immunologic Adjuvants with Low Haemolytic EffectCHEMISTRY & BIODIVERSITY, Issue 7 2006Hong-Xiang Sun Abstract The further purification of the total saponins from the roots of Panax notoginseng (Burk.) F.,H. Chen by ordinary and reversed-phase silica-gel, as well as Sephadex LH-20 chromatography afforded two adjuvant active dammarane-type saponins, ginsenoside Re (1) and notoginsenoside R1 (2). These two saponins were evaluated for haemolytic activities and adjuvant potentials on the cellular and humoral immune responses of ICR mice against ovalbumin (OVA). The concentrations inducing 50% of the maximum haemolysis (HD50), using 0.5% red blood cell suspensions, were 469.6±16.9 and 420.4±22.9 ,g/ml for 1 and 2, respectively. Compounds 1 and 2 significantly increased the concanavalin A (Con A)-, lipopolysaccharide (LPS)-, and OVA-induced splenocyte proliferation in the OVA-immunized mice (P<0.05, P<0.01, or P<0.001). The OVA-specific IgG, IgG1, and IgG2b antibody titres in serum were also significantly enhanced by 1 and 2 compared with OVA control group (P<0.05, P<0.01, or P<0.001). The results indicate that 1 and 2 showed a slight haemolytic activity and significant adjuvant effect on specific antibody and cellular immune response against OVA in mice, and that the type of the terminal sugar of the sugar chain at C(6) of protopanaxatriol could not only affect their haemolytic activities and adjuvant potentials, but have significant effects on the nature of the immune responses. The information about this structurefunction relationship might be useful for developing semisynthetic dammarane-type saponin derivatives with immunological adjuvant activity. [source] Response of Listeria monocytogenes to liquid smokeJOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008M. Guilbaud Abstract Aims:, To investigate the effect of liquid smoke on growth, survival, proteomic pattern and haemolytic potential of Listeria monocytogenes. Methods and Results:, Growth and survival curves were recorded in brain,heart infusion broth supplemented with three concentrations of liquid smoke. L. monocytogenes growth was inhibited in the presence of 15 ,g ml,1 phenol while a rapid decrease in cell viability occurred in the presence of 30 ,g ml,1 phenol. The proteome of L. monocytogenes cytosoluble proteins was slightly modified after 2-h incubation with 30 ,g ml,1 phenol but no protein already characterized in response to other known stresses was induced, except the protease ClpP. Liquid smoke inhibited the haemolytic potential without affecting hly gene expression, showing a potential inhibition of protein activity or stability. Conclusions:, The presence of liquid smoke in a rich medium strongly affected growth and survival of L. monocytogenes. Brief smoke stress affected the metabolic pathways and inhibited the haemolytic activity of L. monocytogenes. Significance and Impact of Study:, This study is a first step in the investigation of the influence of a smoked product on L. monocytogenes strains. [source] Phenotypical characteristics of Shiga-like toxin Escherichia coli isolated from sheep dairy productsLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2007I. Caro Abstract Aims: To analyse phenotypical characteristics of Shiga toxin-producing Escherichia coli (STEC) strains from ovine origin. Methods and Results: A total of 13 STEC strains (eight O157 and five non-O157) isolated from sheep dairy products were used in this study. Biochemical traits, motility, haemolytic activity, resistance to tellurite,cefixime, maximum growth temperature and antibiotic resistance were determined. The STEC strains were grouped into nine biochemical and physiological biotypes (five for the O157 and four for the non-O157 strains). All STEC strains showed resistance to bacitracin, cloxacilin, penicillin and tylosin. Conclusions: Different biotypes and antibiotic resistance patterns of STEC isolated from sheep dairy products were observed. Significance and Impact of the Study: This work will be a contribution to the better characterization of STEC isolated from sheep dairy products, which have, to date, been scarcely studied, and to the better understanding of the risks associated with its consumption. [source] Mutation in the LPS outer core biosynthesis gene, galU, affects LPS interaction with the RTX toxins ApxI and ApxII and cytolytic activity of Actinobacillus pleuropneumoniae serotype 1MOLECULAR MICROBIOLOGY, Issue 1 2008Mahendrasingh Ramjeet Summary Lipopolysaccharides (LPS) and Apx toxins are major virulence factors of Actinobacillus pleuropneumoniae, a pathogen of the respiratory tract of pigs. Here, we evaluated the effect of LPS core truncation in haemolytic and cytotoxic activities of this microorganism. We previously generated a highly attenuated galU mutant of A. pleuropneumoniae serotype 1 that has an LPS molecule lacking the GalNAc-Gal II-Gal I outer core residues. Our results demonstrate that this mutant exhibits wild-type haemolytic activity but is significantly less cytotoxic to porcine alveolar macrophages. However, no differences were found in gene expression and secretion of the haemolytic and cytotoxic toxins ApxI and ApxII, both secreted by A. pleuropneumoniae serotype 1. This suggests that the outer core truncation mediated by the galU mutation affects the toxins in their cytotoxic activities. Using both ELISA and surface plasmon resonance binding assays, we demonstrate a novel interaction between LPS and the ApxI and ApxII toxins via the core oligosaccharide. Our results indicate that the GalNAc-Gal II-Gal I trisaccharide of the outer core is fundamental to mediating LPS/Apx interactions. The present study suggests that a lack of binding between LPS and ApxI/II affects the cytotoxicity and virulence of A. pleuropneumoniae. [source] Oligopeptide permease is required for expression of the Bacillus thuringiensis plcR regulon and for virulenceMOLECULAR MICROBIOLOGY, Issue 4 2001Myriam Gominet PlcR is a pleiotropic regulator of virulence factors in the insect pathogen Bacillus thuringiensis and in the opportunistic human pathogen Bacillus cereus. It activates the transcription of at least 15 genes encoding extracellular proteins, including phospholipases C, proteases and enterotoxins. Expression of the plcR gene is autoregulated and activated at the onset of stationary phase. Here, we used mini-Tn10 transposition to generate a library of B. thuringiensis mutants, with the goal of characterizing genes involved in the expression of the plcR gene. Three mutant strains were identified carrying distinct mini-Tn10 insertions. The mutations impaired plcR expression and caused a deficient haemolytic phenotype, similar to the phenotype of a B. thuringiensis strain in which the plcR gene had been disrupted. The insertion sites of the three mini-Tn10 transposons mapped in a five-gene operon encoding polypeptides homologous to the components of the oligopeptide permease (Opp) system of Bacillus subtilis, and with a similar structural organization. By analogy, the five B. thuringiensis genes were designated oppA, B, C, D and F. In vitro disruption of the B. thuringiensis oppB gene reproduced the effect of the mini-Tn10 insertions (i.e. the loss of haemolytic activity) and reduced the virulence of the strain against insects. These phenotypes are similar to those of a ,plcR mutant. Opp is required for the import of small peptides into the cell. Therefore, plcR expression might be activated at the onset of stationary phase by the uptake of a signalling peptide acting as a quorum-sensing effector. The opp mutations impaired the sporulation efficiency of B. thuringiensis when the cells were cultured in LB medium. Thus, Opp is on the pathway that ultimately regulates Spo0A phosphorylation, as is the case in B. subtilis. However, analysis of plcR expression in ,oppB, ,spo0A and ,oppB,spo0A mutants indicates that Opp is required for plcR expression via a Spo0A-independent mechanism. [source] ESX-1-dependent cytolysis in lysosome secretion and inflammasome activation during mycobacterial infectionCELLULAR MICROBIOLOGY, Issue 9 2008Ingrid C. Koo Summary Exocytosis of lysosomes from macrophages has been described as a response to microbial cytotoxins and haemolysins, as well as for releasing pro-inflammatory cytokines interleukin (IL)-1, and IL-18 during inflammasome activation. The mycobacterial ESX-1 secretion system, encoded in part by the Region of Difference-1, is a virulence factor necessary for phagosome escape and host cell lysis by a contact-dependent haemolysin in Mycobacterium marinum. Here we show that ESX-1 from M. marinum and M. tuberculosis is required for Ca2+ -dependent induction of lysosome secretion from macrophages. Mycobacteria-induced lysosome secretion was concurrent to release of IL-1, and IL-18, dependent on phagocytosis of bacteria containing ESX-1. Synthesis but not release of IL-1, and IL-18 occurred in response to dead bacilli and bacteria lacking ESX-1, indicating that only cytokine release was regulated by ESX-1. Release of these cytokines and exocytosis of lysosomes were independent of intracellular mycobacterial growth, yet correlated with mycobacteria-encoded haemolytic activity, demonstrating a parallel pathway for the two responses. We further identified inflammasome components caspase-1, ASC and NALP3, but not Ipaf, required for release of IL-1, and IL-18. Collectively, these results reveal a role for ESX-1 in triggering secretion of lysosomes, as well as release of IL-1, and IL-18 during mycobacteria infection. [source] New indolicidin analogues with potent antibacterial activity,CHEMICAL BIOLOGY & DRUG DESIGN, Issue 5 2004T.S. Ryge Abstract:, Indolicidin is a 13-residue antimicrobial peptide amide, ILPWKWPWWPWRR-NH2, isolated from the cytoplasmic granules of bovine neutrophils. Indolicidin is active against a wide range of microorganisms and has also been shown to be haemolytic and cytotoxic towards erythrocytes and human T lymphocytes. The aim of the present paper is two-fold. First, we examine the importance of tryptophan in the antibacterial activity of indolicidin. We prepared five peptide analogues with the format ILPXKXPXXPXRR-NH2 in which Trp-residues 4,6,8,9,11 were replaced in all positions with X = a single non-natural building block; N -substituted glycine residue or nonproteinogenic amino acid. The analogues were tested for antibacterial activity against both Staphylococcus aureus American type culture collection (ATCC) 25923 and Escherichia coli ATCC 25922. We found that tryptophan is not essential in the antibacterial activity of indolicidin, and even more active analogues were obtained by replacing tryptophan with non-natural aromatic amino acids. Using this knowledge, we then investigated a new principle for improving the antibacterial activity of small peptides. Our approach involves changing the hydrophobicity of the peptide by modifying the N-terminus with a hydrophobic non-natural building block. We prepared 22 analogues of indolicidin and [Phe4,6,8,9,11] indolicidin, 11 of each, carrying a hydrophobic non-natural building block attached to the N-terminus. Several active antibacterial analogues were identified. Finally, the cytotoxicity of the analogues against sheep erythrocytes was assessed in a haemolytic activity assay. The results presented here suggest that modified analogues of antibacterial peptides, containing non-natural building blocks, are promising lead structures for developing future therapeutics. [source] Ginsenoside Re and Notoginsenoside R1: Immunologic Adjuvants with Low Haemolytic EffectCHEMISTRY & BIODIVERSITY, Issue 7 2006Hong-Xiang Sun Abstract The further purification of the total saponins from the roots of Panax notoginseng (Burk.) F.,H. Chen by ordinary and reversed-phase silica-gel, as well as Sephadex LH-20 chromatography afforded two adjuvant active dammarane-type saponins, ginsenoside Re (1) and notoginsenoside R1 (2). These two saponins were evaluated for haemolytic activities and adjuvant potentials on the cellular and humoral immune responses of ICR mice against ovalbumin (OVA). The concentrations inducing 50% of the maximum haemolysis (HD50), using 0.5% red blood cell suspensions, were 469.6±16.9 and 420.4±22.9 ,g/ml for 1 and 2, respectively. Compounds 1 and 2 significantly increased the concanavalin A (Con A)-, lipopolysaccharide (LPS)-, and OVA-induced splenocyte proliferation in the OVA-immunized mice (P<0.05, P<0.01, or P<0.001). The OVA-specific IgG, IgG1, and IgG2b antibody titres in serum were also significantly enhanced by 1 and 2 compared with OVA control group (P<0.05, P<0.01, or P<0.001). The results indicate that 1 and 2 showed a slight haemolytic activity and significant adjuvant effect on specific antibody and cellular immune response against OVA in mice, and that the type of the terminal sugar of the sugar chain at C(6) of protopanaxatriol could not only affect their haemolytic activities and adjuvant potentials, but have significant effects on the nature of the immune responses. The information about this structurefunction relationship might be useful for developing semisynthetic dammarane-type saponin derivatives with immunological adjuvant activity. [source] | |||||||||||||