Membrane permeabilisation and antimycoplasmic activity of the 18-residue peptaibols, trichorzins PA

AbstractThe membrane permeabilisation properties of six linear natural 18-residue peptaibols, termed trichorzins PA, have been assessed on liposomes and on mollicutes (trivial name, mycoplasmas), a class of parasitic bacteria characterized by a small genome, the lack of a cell wall, a minute cell size, and the incorporation in their plasma membrane of exogenously supplied cholesterol. The trichorzins PA used in this study (PA II, PA IV–VI, PA VIII, and PA IX) differ between them by amino acid or amino alcohol substitutions at positions 4, 7, and 18, and form slightly amphipathic α-helices. They proved bactericidal for mollicutes belonging to the genera Acholeplasma, Mycoplasma, and Spiroplasma, with minimal inhibitory concentrations (3.12≤MICs≤50 μM) generally 2 to 4 fold higher than those of alamethicin F50, a related 20-residue peptide (1.56≤MICs≤12.5 μM). Spiroplasma cells were apparently not protected by the presence of spiralin on their surface. The activities of the six trichorzins PA were not influenced by their sequence variations and no synergistic effect was observed. Consistent with the marginal effect of cholesterol on the incorporation of the trichorzins PA into liposome bilayers, the antibiotic activity was independent of the amount of cholesterol in the membranes of the different mollicutes. The trichorzins PA and alamethicin inhibited the motility of Spiroplasma melliferum, the helical cells being deformed and split into coccoid forms. Membrane potential measurements in Acholeplasma laidlawii and S. melliferum showed that trichorzin PA V and alamethicin F50 very efficiently depolarized the plasma membrane of mollicutes. This was consistent with fluorescence and 23Na NMR measurements on liposomes that revealed the permeabilisation of the lipid bilayer and the nonselective ionophoric activity of the trichorzins PA. These data suggest that the bactericidal activity exhibited by the trichorzins PA on mollicutes is due to the permeabilisation of the plasma membrane

Gastrointestinal stability and cytotoxicity of bacteriocins from gram-positive and gram-negative bacteria : a comparative in vitro study

Bacteriocins are receiving increased attention as potent candidates in food preservation and medicine. Although the inhibitory activity of bacteriocins has been studied widely, little is known about their gastrointestinal stability and toxicity toward normal human cell lines. The aim of this study was to evaluate the gastrointestinal stability and activity of microcin J25, pediocin PA-1, bactofencin A and nisin using in vitro models. In addition cytotoxicity and hemolytic activity of these bacteriocins were investigated on human epithelial colorectal adenocarcinoma cells (Caco-2) and rat erythrocytes, respectively. Pediocin PA-1, bactofencin A, and nisin were observed to lose their stability while passing through the gastrointestinal tract, while microcin J25 is only partially degraded. Besides, selected bacteriocins were not toxic to Caco-2 cells, and integrity of cell membrane was observed to remain unaffected in presence of these bacteriocins at concentrations up to 400 µg/mL. In hemolysis study, pediocin PA-1, bactofencin A, and nisin were observed to lyse rat erythrocytes at concentrations higher than 50 µg/mL, while microcin J25 showed no effect on these cells. According to data indicating gastrointestinal degradation and the absence of toxicity of pediocin PA-1, bactofencin A, and microcin J25 they could potentially be used in food or clinical applications

Fate and Biological Activity of the Antimicrobial Lasso Peptide Microcin J25 Under Gastrointestinal Tract Conditions

The bacteriocin microcin J25 (MccJ25) inhibits the growth of Gram-negative pathogens including Salmonella and Shigella species, and Escherichia coli. This 21-amino acid peptide has remarkable stability to heat and extreme pH values and resistance to many proteases, thanks to a characteristic lasso structure. In this study, we used the dynamic simulator TIM-1 as gastro-intestinal tract model to evaluate the stability and antibacterial activity of MccJ25 during passage through the proximal portion of the human gastrointestinal tract. MccJ25 concentration was measured in the different simulator sections by HPLC, and inhibition of Salmonella enterica serotype Enteritidis was evaluated using qualitative and quantitative assays. LC-MS/MS analysis and subsequent molecular networking analysis on the Global Natural Product Social Molecular Networking platform (GNPS) and analysis of the peptide degradation in the presence of proteolytic enzymes mimicking the gastro-intestinal conditions permitted to delineate the fate of MccJ25 through identification of the main degradation products. MccJ25 was relatively stable under gastric conditions, but degraded rapidly in the compartment mimicking the duodenum, notably in the presence of pancreatin. Among pancreatin components, elastase I appeared primarily responsible for MccJ25 breakdown, while α-chymotrypsin was less efficient

Use of 2,6-diaminopurine as a potent suppressor of UGA premature stop codons in cystic fibrosis

Nonsense mutations are responsible for around 10% of cases of genetic diseases, including cystic fibrosis. 2,6-diaminopurine (DAP) has recently been shown to promote efficient readthrough of UGA premature stop codons. In this study, we show that DAP can correct a nonsense mutation in the Cftr gene in vivo in a new CF mouse model, in utero, and through breastfeeding, thanks, notably, to adequate pharmacokinetic properties. DAP turns out to be very stable in plasma and is distributed throughout the body. The ability of DAP to correct various endogenous UGA nonsense mutations in the CFTR gene and to restore its function in mice, in organoids derived from murine or patient cells, and in cells from patients with cystic fibrosis reveals the potential of such readthrough-stimulating molecules in developing a therapeutic approach. The fact that correction by DAP of certain nonsense mutations reaches a clinically relevant level, as judged from previous studies, makes the use of this compound all the more attractive

Peptides antimicrobiens des entérobactéries (la microcine E492 est un peptide-sidérophore qui parasite les voies d'import du fer)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Peptides antimicrobiens des entérobactéries (étude de la voie de maturation et du mécanisme d'import de la microcine J25, peptide antimicrobien inhibiteur de l ARN polymérase)

MccJ25 est un peptide antibactérien dont la structure tridimensionnelle en forme de lasso résulte du clivage de son précurseur McjA, et de la formation d une liaison Gly1-Glu8 sur le peptide C-terminal résultant. L étude du mode d import bactérien de MccJ25 a montré qu elle parasite un transporteur du complexe fer/ferrichrome, FhuA. MccJ25 se lie à FhuA avec un Kd de 1.2 M, pour former un complexe de stœchiométrie 2:1. La région Val11-Pro16 en épingle à cheveu de MccJ25 est nécessaire à cette interaction. L étude de la biosynthèse de MccJ25 a montré que les gènes mcjB et mcjC du cluster génétique de MccJ25 sont nécessaires à la production de MccJ25 mature. La production de McjA, McjB et McjC recombinantes a permis de montrer que McjB et McjC sont capables de catalyser la conversion de McjA en MccJ25 structurée en lasso. L étude des similarités de séquences de McjB et McjC indique que McjB réaliserait le clivage protéolytique de McjA et McjC formerait la liaison Gly1-Glu8.PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Les microcines C51 et J25, peptides antimicrobiens d'Entérobactéries (études structurales par RMN et modélisation moléculaire)

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Peptides antimicrobiens de procaryotes et d'eucaryotes (des structures aux mécanismes d'action)

PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

The manifold roles of microbial ribosomal peptide–based natural products in physiology and ecology

International audienc