Membrane activities of colicin nuclease domains: analogies with antimicrobial peptides

2012 ◽  
Vol 40 (6) ◽  
pp. 1517-1521 ◽  
Author(s):  
Mireille Vankemmelbeke ◽  
Richard James ◽  
Christopher N. Penfold
Keyword(s):  
Antimicrobial Peptides ◽  
Molecular Mechanisms ◽  
Gram Negative Bacteria ◽  
Membrane Translocation ◽  
Insertion Depth ◽  
E Coli ◽  
Ongoing Work ◽  
Colicin E9 ◽  
Bilayer Permeability

Nuclease colicins, such as colicin E9, are a class of Escherichia coli bacteriocins that kill E. coli and closely related Gram-negative bacteria through nucleolytic action in the cytoplasm. In order to accomplish this, their cytotoxic domains require transportation across two sets of membranes and the periplasmic space. Currently, little information is available concerning how the membrane translocation processes are achieved, and the present review summarizes our recent results on the in vitro membrane activities of the colicin nuclease domains. Using model membranes, we have analysed the cytotoxic domains of a number of DNase-type colicins and one rRNase colicin for their bilayer insertion depth and for their ability to induce vesicle aggregation, lipid mixing and increased bilayer permeability. We found that, by analogy with AMPs (antimicrobial peptides), the interplay between charge and hydrophobic character of the nuclease domains governs their pleiotropic membrane activities and these results form the basis of ongoing work to unravel the molecular mechanisms underlying their membrane translocation.

scholarly journals Proteomic response of Escherichia coli to a membrane lytic and iron chelating truncated Amaranthus tricolor defensin

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Tessa B. Moyer ◽  
Ashleigh L. Purvis ◽  
Andrew J. Wommack ◽  
Leslie M. Hicks
Keyword(s):  
Escherichia Coli ◽  
Antibacterial Activity ◽  
Antimicrobial Peptides ◽  
Mechanism Of Action ◽  
Gram Negative Bacteria ◽  
Amaranthus Tricolor ◽  
Core Motif ◽  
Gram Negative ◽  
E Coli ◽  
Membrane Lysis

Abstract Background Plant defensins are a broadly distributed family of antimicrobial peptides which have been primarily studied for agriculturally relevant antifungal activity. Recent studies have probed defensins against Gram-negative bacteria revealing evidence for multiple mechanisms of action including membrane lysis and ribosomal inhibition. Herein, a truncated synthetic analog containing the γ-core motif of Amaranthus tricolor DEF2 (Atr-DEF2) reveals Gram-negative antibacterial activity and its mechanism of action is probed via proteomics, outer membrane permeability studies, and iron reduction/chelation assays. Results Atr-DEF2(G39-C54) demonstrated activity against two Gram-negative human bacterial pathogens, Escherichia coli and Klebsiella pneumoniae. Quantitative proteomics revealed changes in the E. coli proteome in response to treatment of sub-lethal concentrations of the truncated defensin, including bacterial outer membrane (OM) and iron acquisition/processing related proteins. Modification of OM charge is a common response of Gram-negative bacteria to membrane lytic antimicrobial peptides (AMPs) to reduce electrostatic interactions, and this mechanism of action was confirmed for Atr-DEF2(G39-C54) via an N-phenylnaphthalen-1-amine uptake assay. Additionally, in vitro assays confirmed the capacity of Atr-DEF2(G39-C54) to reduce Fe3+ and chelate Fe2+ at cell culture relevant concentrations, thus limiting the availability of essential enzymatic cofactors. Conclusions This study highlights the utility of plant defensin γ-core motif synthetic analogs for characterization of novel defensin activity. Proteomic changes in E. coli after treatment with Atr-DEF2(G39-C54) supported the hypothesis that membrane lysis is an important component of γ-core motif mediated antibacterial activity but also emphasized that other properties, such as metal sequestration, may contribute to a multifaceted mechanism of action.

Formation, translocation and resolution of Holliday junctions during homologous genetic recombination

1995 ◽  
Vol 347 (1319) ◽  
pp. 21-25 ◽  
Keyword(s):  
Molecular Mechanisms ◽  
Genetic Recombination ◽  
Holliday Junctions ◽  
The Novel ◽  
E Coli ◽  
The Past ◽  
Endonucleolytic Cleavage ◽  
Insight Into ◽  
Made In

Over the past three or four years, great strides have been made in our understanding of the proteins involved in recombination and the mechanisms by which recombinant molecules are formed. This review summarizes our current understanding of the process by focusing on recent studies of proteins involved in the later steps of recombination in bacteria. In particular, biochemical investigation of the in vitro properties of the E. coli RuvA, RuvB and RuvC proteins have provided our first insight into the novel molecular mechanisms by which Holliday junctions are moved along DNA and then resolved by endonucleolytic cleavage.

scholarly journals Interaction of Antimicrobial Peptide Temporin L with Lipopolysaccharide In Vitro and in Experimental Rat Models of Septic Shock Caused by Gram-Negative Bacteria

2006 ◽  
Vol 50 (7) ◽  
pp. 2478-2486 ◽  
Author(s):  
Andrea Giacometti ◽  
Oscar Cirioni ◽  
Roberto Ghiselli ◽  
Federico Mocchegiani ◽  
Fiorenza Orlando ◽  
...  
Keyword(s):  
Septic Shock ◽  
Antimicrobial Peptide ◽  
Gram Negative Bacteria ◽  
Amphibian Skin ◽  
Necrosis Factor Alpha ◽  
Gram Negative ◽  
Rat Models ◽  
E Coli ◽  
Tnf Α

ABSTRACT Sepsis remains a major cause of morbidity and mortality in hospitalized patients, despite intense efforts to improve survival. The primary lead for septic shock results from activation of host effector cells by endotoxin, the lipopolysaccharide (LPS) associated with cell membranes of gram-negative bacteria. For these reasons, the quest for compounds with antiendotoxin properties is actively pursued. We investigated the efficacy of the amphibian skin antimicrobial peptide temporin L in binding Escherichia coli LPS in vitro and counteracting its effects in vivo. Temporin L strongly bound to purified E. coli LPS and lipid A in vitro, as proven by fluorescent displacement assay, and readily penetrated into E. coli LPS monolayers. Furthermore, the killing activity of temporin L against E. coli was progressively inhibited by increasing concentrations of LPS added to the medium, further confirming the peptide's affinity for endotoxin. Antimicrobial assays showed that temporin L interacted synergistically with the clinically used β-lactam antibiotics piperacillin and imipenem. Therefore, we characterized the activity of temporin L when combined with imipenem and piperacillin in the prevention of lethality in two rat models of septic shock, measuring bacterial growth in blood and intra-abdominal fluid, endotoxin and tumor necrosis factor alpha (TNF-α) concentrations in plasma, and lethality. With respect to controls and single-drug treatments, the simultaneous administration of temporin L and β-lactams produced the highest antimicrobial activities and the strongest reduction in plasma endotoxin and TNF-α levels, resulting in the highest survival rates.

Abstract 066: The Undescribed Protein Caskin2 Is a Novel Regulator of eNOS Phosphorylation and Systemic Blood Pressure

Hypertension ◽  
2015 ◽  
Vol 66 (suppl_1) ◽  
Author(s):  
Sarah B Mueller ◽  
Susan B Gurley ◽  
Christopher D Kontos
Keyword(s):  
Blood Pressure ◽  
Molecular Mechanisms ◽  
Systemic Blood Pressure ◽  
Regulatory Subunit ◽  
Systemic Blood ◽  
Homologous Expression ◽  
Ongoing Work ◽  
Inducing Factors

Disruptions in the function of the quiescent endothelial cells (ECs) that line mature vessels can both result in and contribute to the progression of numerous cardiovascular diseases including hypertension, atherosclerosis, and disorders of vascular permeability. Despite recent attention, the signaling pathways that are active in quiescent ECs remain poorly characterized relative to those that regulate EC activation. In an effort to provide mechanistic insight into these pathways, we have characterized the previously undescribed protein Caskin2, which we hypothesize is a novel regulator of EC quiescence. Caskin2 is expressed in ECs throughout the vasculature, including the aorta, coronary arteries, and renal glomeruli. In vitro, Caskin2 promotes a quiescent EC phenotype characterized by decreased proliferation and increased resistance to apoptosis-inducing factors. Caskin2 knockout mice are viable and fertile. However, preliminary radiotelemetry measurements indicate that Caskin2 knockout (KO) mice have mildly elevated systemic blood pressure (BP). Compared to wild type (WT) littermates (n=8), Caskin2 KO mice (n=7) had increased mean arterial pressure (119+/-1 vs. 113+/-1, p=0.012), systolic BP (138+/-2 vs. 132+/-2, p=0.023), and diastolic BP (99+/-1 vs. 93+/-1, p=0.014) at baseline. To explore the molecular mechanisms of Caskin2’s effects, we used mass spectrometry to identify interacting proteins. Among the 67 proteins identified were the Ser/Thr phosphatase protein phosphatase 1 (PP1) and eNOS. Using standard in vitro biochemical techniques, we demonstrated that Caskin2 acts as a PP1 regulatory subunit. Interestingly, homologous expression of Caskin2 in vitro resulted in a marked increase in phosphorylation of eNOS on S1177, which is known to promote eNOS activity, and a decrease in phosphorylation on T495, which is associated with eNOS inhibition. Finally, PP1 has been shown to dephosphorylate eNOS T495 in vitro, suggesting a molecular mechanism for our in vivo findings. Ongoing work aims to determine if the interaction of Caskin2 and PP1 is required for the Caskin2-induced increase in activating phosphorylation of eNOS and to characterize the physiological mechanisms responsible for Caskin2’s effects on BP in more detail.

scholarly journals Synergy and remarkable specificity of antimicrobial peptides in vivo using a systematic knockout approach

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Mark Austin Hanson ◽  
Anna Dostálová ◽  
Camilla Ceroni ◽  
Mickael Poidevin ◽  
Shu Kondo ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Fungal Pathogens ◽  
Gene Editing ◽  
Cationic Peptides ◽  
Gram Negative Bacteria ◽  
Biological Processes ◽  
Gram Negative ◽  
Bacteria And Fungi

Antimicrobial peptides (AMPs) are host-encoded antibiotics that combat invading microorganisms. These short, cationic peptides have been implicated in many biological processes, primarily involving innate immunity. In vitro studies have shown AMPs kill bacteria and fungi at physiological concentrations, but little validation has been done in vivo. We utilized CRISPR gene editing to delete most known immune-inducible AMPs of Drosophila, namely: 4 Attacins, 2 Diptericins, Drosocin, Drosomycin, Metchnikowin and Defensin. Using individual and multiple knockouts, including flies lacking these ten AMP genes, we characterize the in vivo function of individual and groups of AMPs against diverse bacterial and fungal pathogens. We found that Drosophila AMPs act primarily against Gram-negative bacteria and fungi, contributing either additively or synergistically. We also describe remarkable specificity wherein certain AMPs contribute the bulk of microbicidal activity against specific pathogens, providing functional demonstrations of highly specific AMP-pathogen interactions in an in vivo setting.

scholarly journals SPS-neutralization in tissue samples for efficacy testing of antimicrobial peptides

2019 ◽  
Vol 19 (1) ◽  
Author(s):  
Gabrielle Sherella Dijksteel ◽  
Peter H. Nibbering ◽  
Magda M. W. Ulrich ◽  
Esther Middelkoop ◽  
Bouke K. H. L. Boekema
Keyword(s):  
Antimicrobial Activity ◽  
Antimicrobial Peptides ◽  
Antimicrobial Agents ◽  
Ex Vivo ◽  
Residual Activity ◽  
Gram Negative Bacteria ◽  
Tissue Samples ◽  
Gram Negative ◽  
Viable Bacteria

Abstract Background Accurate determination of the efficacy of antimicrobial agents requires neutralization of residual antimicrobial activity in the samples before microbiological assessment of the number of surviving bacteria. Sodium polyanethol sulfonate (SPS) is a known neutralizer for the antimicrobial activity of aminoglycosides and polymyxins. In this study, we evaluated the ability of SPS to neutralize residual antimicrobial activity of antimicrobial peptides [SAAP-148 and pexiganan; 1% (wt/v) in PBS], antibiotics [mupirocin (Bactroban) and fusidic acid (Fucidin) in ointments; 2% (wt/wt))] and disinfectants [2% (wt/wt) silver sulfadiazine cream (SSD) and 0.5% (v/v) chlorhexidine in 70% alcohol]. Methods Homogenates of human skin models that had been exposed to various antimicrobial agents for 1 h were pipetted on top of Methicillin-resistant Staphylococcus aureus (MRSA) on agar plates to determine whether the antimicrobial agents display residual activity. To determine the optimal concentration of SPS for neutralization, antimicrobial agents were mixed with PBS or increasing doses of SPS in PBS (0.05–1% wt/v) and then 105 colony forming units (CFU)/mL MRSA were added. After 30 min incubation, the number of viable bacteria was assessed. Next, the in vitro efficacy of SAAP-148 against various gram-positive and gram-negative bacteria was determined using PBS or 0.05% (wt/v) SPS immediately after 30 min incubation of the mixture. Additionally, ex vivo excision wound models were inoculated with 105 CFU MRSA for 1 h and exposed to SAAP-148, pexiganan, chlorhexidine or PBS for 1 h. Subsequently, samples were homogenized in PBS or 0.05% (wt/v) SPS and the number of viable bacteria was assessed. Results All tested antimicrobials displayed residual activity in tissue samples, resulting in a lower recovery of surviving bacteria on agar. SPS concentrations at ≥0.05% (wt/v) were able to neutralize the antimicrobial activity of SAAP-148, pexiganan and chlorhexidine, but not of SSD, Bactroban and Fucidin. Finally, SPS-neutralization in in vitro and ex vivo efficacy tests of SAAP-148, pexiganan and chlorhexidine against gram-positive and gram-negative bacteria resulted in significantly higher numbers of CFU compared to control samples without SPS-neutralization. Conclusions SPS was successfully used to neutralize residual activity of SAAP-148, pexiganan and chlorhexidine and this prevented an overestimation of their efficacy.

scholarly journals Lipocalin 2: A New Antimicrobial in Mast Cells

2019 ◽  
Vol 20 (10) ◽  
pp. 2380 ◽  
Author(s):  
Yu-Ling Chang ◽  
Zhenping Wang ◽  
Satomi Igawa ◽  
Jae Eun Choi ◽  
Tyler Werbel ◽  
...  
Keyword(s):  
Mast Cells ◽  
Antimicrobial Peptides ◽  
Antimicrobial Peptide ◽  
Bacterial Growth ◽  
Immune Defense ◽  
Lipocalin 2 ◽  
Vitro Assay ◽  
E Coli ◽  
Sphingosine 1 Phosphate

Mast cells (MCs) play a significant role in the innate immune defense against bacterial infection through the release of cytokines and antimicrobial peptides. However, their antimicrobial function is still only partially described. We therefore hypothesized that MCs express additional antimicrobial peptides. In this study, we used FANTOM 5 transcriptome data to identify for the first time that MCs express lipocalin 2 (LCN2), a known inhibitor of bacterial growth. Using MCs derived from mice which were deficient in LCN2, we showed that this antimicrobial peptide is an important component of the MCs’ antimicrobial activity against Escherichia coli (E. coli). Since sphingosine-1-phosphate receptors (S1PRs) on MCs are known to regulate their function during infections, we hypothesized that S1P could activate LCN2 production in MCs. Using an in vitro assay, we demonstrated that S1P enhances MCs antimicrobial peptide production and increases the capacity of MCs to directly kill S. aureus and E. coli via an LCN2 release. In conclusion, we showed that LCN2 is expressed by MCs and plays a role in their capacity to inhibit bacterial growth.

Synthesis and in vitro Biological Activity of New 4,6-Disubstituted 3(2H)-Pyridazinone-acetohydrazide Derivatives

2012 ◽  
Vol 67 (5-6) ◽  
pp. 257-265
Author(s):  
Murat Sukuroglu ◽  
Tijen Onkol ◽  
Fatma Kaynak Onurdağ ◽  
Gulsen Akalın ◽  
M. Fethi Şahin
Keyword(s):  
Biological Activity ◽  
Antimicrobial Activities ◽  
Cytotoxic Activities ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
E Coli ◽  
Preliminary Results ◽  
H Nmr ◽  
Pyridazinone Derivatives

New 3(2H)-pyridazinone derivatives containing a N’-benzyliden-acetohydrazide moiety at position 2 were synthesized. The structures of these newly synthesized compounds were confi rmed by IR, 1H NMR, and MS data. These compounds were tested for their antibacterial, antifungal, antimycobacterial, and cytotoxic activities. The compounds 2-[4-(4-chlorophenyl)- 6-(morpholin-4-yl)-3-oxo-(2H)-pyridazin-2-yl]-N’-(4-tert-butylbenzyliden)acetohydrazide and 2-[4-(4-chlorophenyl)-6-(morpholin-4-yl)-3-oxo-(2H)-pyridazin-2-yl]-N’-(4-chlorobenzyliden) acetohydrazide exhibited activity against both Gram-positive and Gram-negative bacteria. Most of the compounds were active against E. coli ATCC 35218. The preliminary results of this study revealed that some target compounds exhibited promising antimicrobial activities

scholarly journals Role of F1C Fimbriae, Flagella, and Secreted Bacterial Components in the Inhibitory Effect of Probiotic Escherichia coli Nissle 1917 on Atypical Enteropathogenic E. coli Infection

2014 ◽  
Vol 82 (5) ◽  
pp. 1801-1812 ◽  
Author(s):  
Sylvia Kleta ◽  
Marcel Nordhoff ◽  
Karsten Tedin ◽  
Lothar H. Wieler ◽  
Rafal Kolenda ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Molecular Mechanisms ◽  
Inhibitory Effect ◽  
Host Cells ◽  
Single Infection ◽  
Content Type ◽  
E Coli ◽  
Initial Adhesion

ABSTRACTEnteropathogenicEscherichia coli(EPEC) is recognized as an important intestinal pathogen that frequently causes acute and persistent diarrhea in humans and animals. The use of probiotic bacteria to prevent diarrhea is gaining increasing interest. The probioticE. colistrain Nissle 1917 (EcN) is known to be effective in the treatment of several gastrointestinal disorders. While bothin vitroandin vivostudies have described strong inhibitory effects of EcN on enteropathogenic bacteria, including pathogenicE. coli, the underlying molecular mechanisms remain largely unknown. In this study, we examined the inhibitory effect of EcN on infections of porcine intestinal epithelial cells with atypical enteropathogenicE. coli(aEPEC) with respect to single infection steps, including adhesion, microcolony formation, and the attaching and effacing phenotype. We show that EcN drastically reduced the infection efficiencies of aEPEC by inhibiting bacterial adhesion and growth of microcolonies, but not the attaching and effacing of adherent bacteria. The inhibitory effect correlated with EcN adhesion capacities and was predominantly mediated by F1C fimbriae, but also by H1 flagella, which served as bridges between EcN cells. Furthermore, EcN seemed to interfere with the initial adhesion of aEPEC to host cells by secretion of inhibitory components. These components do not appear to be specific to EcN, but we propose that the strong adhesion capacities enable EcN to secrete sufficient local concentrations of the inhibitory factors. The results of this study are consistent with a mode of action whereby EcN inhibits secretion of virulence-associated proteins of EPEC, but not their expression.

scholarly journals Trends in the Susceptibility of Clinically Important Resistant Bacteria to Tigecycline: Results from the TigecyclineIn VitroSurveillance in Taiwan Study, 2006 to 2010

2011 ◽  
Vol 56 (3) ◽  
pp. 1452-1457 ◽  
Author(s):  
Yen-Hsu Chen ◽  
Po-Liang Lu ◽  
Cheng-Hua Huang ◽  
Chun-Hsing Liao ◽  
Chin-Te Lu ◽  
...  
Keyword(s):  
Resistant Bacteria ◽  
Gram Negative Bacteria ◽  
Drug Resistant ◽  
Content Type ◽  
E Coli ◽  
Drug Resistant Bacteria ◽  
Vancomycin Resistant ◽  
Susceptibility Rate ◽  
Important Drug

ABSTRACTThe TigecyclineIn VitroSurveillance in Taiwan (TIST) study, a nationwide, prospective surveillance during 2006 to 2010, collected a total of 7,793 clinical isolates, including methicillin-resistantStaphylococcus aureus(MRSA) (n= 1,834), penicillin-resistantStreptococcus pneumoniae(PRSP) (n= 423), vancomycin-resistant enterococci (VRE) (n= 219), extended-spectrum β-lactamase (ESBL)-producingEscherichia coli(n= 1,141), ESBL-producingKlebsiella pneumoniae(n= 1,330),Acinetobacter baumannii(n= 1,645), andStenotrophomonas maltophilia(n= 903), from different specimens from 20 different hospitals in Taiwan. MICs of tigecycline were determined following the criteria of the U.S. Food and Drug Administration (FDA) and the European Committee on Antimicrobial Susceptibility Testing (EUCAST-2011). Among drug-resistant Gram-positive pathogens, all of the PRSP isolates were susceptible to tigecycline (MIC90, 0.03 μg/ml), and only one MRSA isolate (MIC90, 0.5 μg/ml) and three VRE isolates (MIC90, 0.125 μg/ml) were nonsusceptible to tigecycline. Among the Gram-negative bacteria, the tigecycline susceptibility rates were 99.65% for ESBL-producingE. coli(MIC90, 0.5 μg/ml) and 96.32% for ESBL-producingK. pneumoniae(MIC90, 2 μg/ml) when interpreted by FDA criteria but were 98.7% and 85.8%, respectively, when interpreted by EUCAST-2011 criteria. The susceptibility rate forA. baumannii(MIC90, 4 μg/ml) decreased from 80.9% in 2006 to 55.3% in 2009 but increased to 73.4% in 2010. A bimodal MIC distribution was found among carbapenem-susceptibleA. baumanniiisolates, and a unimodal MIC distribution was found among carbapenem-nonsusceptibleA. baumanniiisolates. In Taiwan, tigecycline continues to have excellentin vitroactivity against several major clinically important drug-resistant bacteria, with the exception ofA. baumannii.

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