scholarly journals Interactions between the plasma membrane and the antimicrobial peptide HP (2-20) and its analogues derived from Helicobacter pylori

2006 ◽  
Vol 394 (1) ◽  
pp. 105-114 ◽  
Author(s):  
Kwang H. Lee ◽  
Dong G. Lee ◽  
Yoonkyung Park ◽  
Dong-Il Kang ◽  
Song Y. Shin ◽  
...  

HP (2-20), a 19-residue peptide derived from the N-terminus of Helicobacter pylori ribosomal protein L1, has antimicrobial activity but is not cytotoxic to human erythrocytes. We synthesized several peptide analogues to investigate the effects of substitutions on structure and antimicrobial activity. Replacement of Gln16 and Asp18 with tryptophan [anal-3 (analogue-3)] caused a dramatic increase in lytic activities against bacteria and fungi. By contrast, a decrease in amphiphilicity caused by replacement of Phe5 or Leu11 with serine was accompanied by a reduction in antimicrobial activity. Analysis of the tertiary structures of the peptides in SDS micelles by NMR spectroscopy revealed that they have a well-defined α-helical structure. Among the analogues, anal-3 has the longest α-helix, from Val4 to Trp18. The enhanced hydrophobicity and increased α-helicity results in enhanced antimicrobial activity in anal-3 without an increase in haemolytic activity. Fluorescence experiments proved that the bacterial-cell selectivity of the anal-3 peptide is due to its high binding affinity for negatively charged phospholipids in bacterial cells. Results showing the effect of spin-labels on the NMR spectra indicated that the side chains in the hydrophobic phase of the amphiphilic α-helix are buried on the surface of the micelle and the tryptophan indole ring is anchored in the membrane surface. Because anal-3 shows high selectivity towards bacterial and fungal cells, it may provide an avenue for the development of new antibiotics.

2021 ◽  
Vol 22 (18) ◽  
pp. 9752
Author(s):  
Sung-Tae Yang ◽  
Song-Yub Shin ◽  
Sung-Heui Shin

PMAP-23, a cathelicidin-derived host defense peptide, does not cause severe membrane permeabilization, but exerts strong and broad-spectrum bactericidal activity. We have previously shown that it forms an amphipathic α-helical structure with a central hinge induced by the PXXP motif, which is implicated in the interaction of PMAP-23 with negatively charged bacterial membranes. Here, we studied the potential roles of the PXXP motif in PMAP-23 translocation across the lipid bilayer by replacing Pro residues with either α-helix former Ala (PMAP-PA) or α-helix breaker Gly (PMAP-PG). Although both PMAP-PA and PMAP-PG led to effective membrane depolarization and permeabilization, they showed less antimicrobial activity than wild-type PMAP-23. Interestingly, we observed that PMAP-23 crossed lipid bilayers much more efficiently than its Pro-substituted derivatives. The fact that the Gly-induced hinge was unable to replace the PXXP motif in PMAP-23 translocation suggests that the PXXP motif has unique structural properties other than the central hinge. Surface plasmon resonance sensorgrams showed that the running buffer almost entirely dissociated PMAP-23 from the membrane surface, while its Pro-substituted derivatives remained significantly bound to the membrane. In addition, kinetic analysis of the sensorgrams revealed that the central PXXP motif allows PMAP-23 to rapidly translocate at the interface between the hydrophilic and hydrophobic phases. Taken together, we propose that the structural and kinetic understanding of the PXXP motif in peptide translocation could greatly aid the development of novel antimicrobial peptides with intracellular targets by promoting peptide entry into bacterial cells.


2018 ◽  
Vol 10 (1) ◽  
pp. 21-25
Author(s):  
Mutyala Naidu LAGUDU ◽  
Aniel Kumar OWK

The phytochemical investigation of the leaves of Litsea glutinosa revealed the presence of secondary metabolites like alkaloids, anthraquinones, cardiac glycosides, flavonoids, glycosides, phenols, saponins, steroids, tannins, terpenoids, volatile compounds, amino acids and carbohiydrates. The antimicrobial activity and minimum inhibition concentration values were determined for these phytochemical constituents as crude extracts using the agar well diffusion and two-fold serial dilution methods. The results indicated that Bacillus subtilis was the most susceptible bacterium with high inhibition zones for the methanol and chloroform extracts of 31 mm and 26 mm, respectively. The MIC values indicated that extracts possess good antimicrobial activity with significant MIC value against Enterococcus faecalis, Pseudomonas aeruginosa and Staphylococcus pneumoniae at 31.2 µg/ml concentrations. The extracts showed marked antimicrobial activity against both bacteria and fungi. Among the bacterial strains, gram-positive bacteria were more susceptible than the gram-negative. All the 13 microorganisms tested showed dose dependent susceptibility towards the phytochemicals present in the foliar extracts. The study suggests that Litsea glutinosa leaves possess potent antimicrobial activity and can be a good source for the development of new antibiotics.


2021 ◽  
Vol 12 ◽  
Author(s):  
Monika Wojciechowska ◽  
Julia Macyszyn ◽  
Joanna Miszkiewicz ◽  
Renata Grzela ◽  
Joanna Trylska

Anoplin is a linear 10-amino acid amphipathic peptide (Gly-Leu-Leu-Lys-Arg-Ile-Lys-Thr-Leu-Leu-NH2) derived from the venom sac of the solitary wasp. It has broad antimicrobial activity, including an antibacterial one. However, the inhibition of bacterial growth requires several dozen micromolar concentrations of this peptide. Anoplin is positively charged and directly interacts with anionic biological membranes forming an α-helix that disrupts the lipid bilayer. To improve the bactericidal properties of anoplin by stabilizing its helical structure, we designed and synthesized its analogs with hydrocarbon staples. The staple was introduced at two locations resulting in different charges and amphipathicity of the analogs. Circular dichroism studies showed that all modified anoplins adopted an α-helical conformation, both in the buffer and in the presence of membrane mimics. As the helicity of the stapled anoplins increased, their stability in trypsin solution improved. Using the propidium iodide uptake assay in Escherichia coli and Staphylococcus aureus, we confirmed the bacterial membrane disruption by the stapled anoplins. Next, we tested the antimicrobial activity of peptides on a range of Gram-negative and Gram-positive bacteria. Finally, we evaluated peptide hemolytic activity on sheep erythrocytes and cytotoxicity on human embryonic kidney 293 cells. All analogs showed higher antimicrobial activity than unmodified anoplin. Depending on the position of the staple, the peptides were more effective either against Gram-negative or Gram-positive bacteria. Anoplin[5-9], with a lower positive charge and increased hydrophobicity, had higher activity against Gram-positive bacteria but also showed hemolytic and destructive effects on eukaryotic cells. Contrary, anoplin[2-6] with a similar charge and amphipathicity as natural anoplin effectively killed Gram-negative bacteria, also pathogenic drug-resistant strains, without being hemolytic and toxic to eukaryotic cells. Our results showed that anoplin charge, amphipathicity, and location of hydrophobic residues affect the peptide destructive activity on the cell wall, and thus, its antibacterial activity. This means that by manipulating the charge and position of the staple in the sequence, one can manipulate the antimicrobial activity.


2019 ◽  
Vol 26 (3) ◽  
pp. 192-203
Author(s):  
María Verónica Húmpola ◽  
María Carolina Rey ◽  
Pablo Gabriel Spontón ◽  
Arturo Carlos Simonetta ◽  
Georgina Guadalupe Tonarelli

Background:In the last years, Antimicrobial Peptides (AMPs) and lipopeptides have received attention as promising candidates to treat infections caused by resistant microorganisms. </P><P> Objective: The main objective of this study was to investigate the effect of repetitive KLFK motifs and the attachment of aliphatic acids to the N-terminus of (KLFK)n peptides on therapeutic properties.Methods:Minimal inhibitory concentration against Gram (+) and (-) bacteria and yeast of synthetic compounds were determined by broth microtiter dilution method, and the toxicity was evaluated by hemolysis assay. Membrane-peptide interaction studies were performed with model phospholipid membranes mimicking those of bacterial and mammalian cells by Fluorescence Spectroscopy. The secondary structure in solution and membranes was determined by Circular Dichroism.Results:Our results showed that the resulting compounds have inhibitory activity against bacteria and fungi. The (KLFK)3 peptide showed the highest therapeutic index against bacterial and yeast strains, and the (KLFK)2 peptide conjugated with octanoic acid was the most active against yeasts. All the lipopeptides containing long-chain fatty acids (C14 or longer) were highly hemolytic at low concentrations. The antimicrobial activity of (KLFK)2 and (KLFK)3 lipopeptides was mainly associated with improved stability of the amphipathic secondary structure, which showed high contributions of α-helix in dipalmitoylphosphatidylglycerol (DPPG) vesicles.Conclusion:The repetition of the KLFK sequence and the conjugation with lipid tails allowed obtained compounds with high antimicrobial activity and low toxicity, becoming good candidates for treating infectious diseases.


Author(s):  
О.В. Шамова ◽  
М.С. Жаркова ◽  
П.М. Копейкин ◽  
Д.С. Орлов ◽  
Е.А. Корнева

Антимикробные пептиды (АМП) системы врожденного иммунитета - соединения, играющие важную роль в патогенезе инфекционных заболеваний, так как обладают свойством инактивировать широкий спектр патогенных бактерий, обеспечивая противомикробную защиту живых организмов. В настоящее время АМП рассматриваются как потенциальные соединения-корректоры инфекционной патологии, вызываемой антибиотикорезистентными бактериями (АБР). Цель данной работы состояла в изученим механизмов антибактериального действия трех пептидов, принадлежащих к семейству бактенецинов - ChBac3.4, ChBac5 и mini-ChBac7.5Nb. Эти химически синтезированные пептиды являются аналогами природных пролин-богатых АМП, обнаруженных в лейкоцитах домашней козы Capra hircus и проявляющих высокую антимикробную активность, в том числе и в отношении грамотрицательных АБР. Методы. Минимальные ингибирующие и минимальные бактерицидные концентрации пептидов (МИК и МБК) определяли методом серийных разведений в жидкой питательной среде с последующим высевом на плотную питательную среду. Эффекты пептидов на проницаемость цитоплазматической мембраны бактерий для хромогенного маркера исследовали с использованием генетически модифицированного штамма Escherichia coli ML35p. Действие бактенецинов на метаболическую активность бактерий изучали с применением маркера резазурина. Результаты. Показано, что все исследованные пептиды проявляют высокую антимикробную активность в отношении Escherichia coli ML35p и антибиотикоустойчивых штаммов Escherichia coli ESBL и Acinetobacter baumannii in vitro, но их действие на бактериальные клетки разное. Использован комплекс методик, позволяющих наблюдать в режиме реального времени динамику действия бактенецинов в различных концентрациях (включая их МИК и МБК) на барьерную функцию цитоплазматической мембраны и на интенсивность метаболизма бактериальных клеток, что дало возможность выявить различия в характере воздействия бактенецинов, отличающихся по структуре молекулы, на исследуемые микроорганизмы. Установлено, что действие каждого из трех исследованных бактенецинов в бактерицидных концентрациях отличается по эффективности нарушения целостности бактериальных мембран и в скорости подавления метаболизма клеток. Заключение. Полученная информация дополнит существующие фундаментальные представления о механизмах действия пролин-богатых пептидов врожденного иммунитета, а также послужит основой для биотехнологических исследований, направленных на разработку на базе этих соединений новых антибиотических препаратов для коррекции инфекционных заболеваний, вызываемых АБР и являющимися причинами тяжелых внутрибольничных инфекций. Antimicrobial peptides (AMPs) of the innate immunity are compounds that play an important role in pathogenesis of infectious diseases due to their ability to inactivate a broad array of pathogenic bacteria, thereby providing anti-microbial host defense. AMPs are currently considered promising compounds for treatment of infectious diseases caused by antibiotic-resistant bacteria. The aim of this study was to investigate molecular mechanisms of the antibacterial action of three peptides from the bactenecin family, ChBac3.4, ChBac5, and mini-ChBac7.5Nb. These chemically synthesized peptides are analogues of natural proline-rich AMPs previously discovered by the authors of the present study in leukocytes of the domestic goat, Capra hircus. These peptides exhibit a high antimicrobial activity, in particular, against antibiotic-resistant gram-negative bacteria. Methods. Minimum inhibitory and minimum bactericidal concentrations of the peptides (MIC and MBC) were determined using the broth microdilution assay followed by subculturing on agar plates. Effects of the AMPs on bacterial cytoplasmic membrane permeability for a chromogenic marker were explored using a genetically modified strain, Escherichia coli ML35p. The effect of bactenecins on bacterial metabolic activity was studied using a resazurin marker. Results. All the studied peptides showed a high in vitro antimicrobial activity against Escherichia coli ML35p and antibiotic-resistant strains, Escherichia coli ESBL and Acinetobacter baumannii, but differed in features of their action on bacterial cells. The used combination of techniques allowed the real-time monitoring of effects of bactenecin at different concentrations (including their MIC and MBC) on the cell membrane barrier function and metabolic activity of bacteria. The differences in effects of these three structurally different bactenecins on the studied microorganisms implied that these peptides at bactericidal concentrations differed in their capability for disintegrating bacterial cell membranes and rate of inhibiting bacterial metabolism. Conclusion. The obtained information will supplement the existing basic concepts on mechanisms involved in effects of proline-rich peptides of the innate immunity. This information will also stimulate biotechnological research aimed at development of new antibiotics for treatment of infectious diseases, such as severe in-hospital infections, caused by antibiotic-resistant strains.


Author(s):  
Kolathuru Puttamadaiah Ramesha ◽  
Nagabhushana Chandra Mohana ◽  
Bettadapura Rameshgowda Nuthan ◽  
Devaraju Rakshith ◽  
Sreedharamurthy Satish

Abstract Background Endophyte bestows beneficial aspects to its inhabiting host, along with a contribution to diverse structural attributes with biological potential. In this regard, antimicrobial profiling of fungal endophytes from medicinal plant Adiantum philippense revealed bioactive Nigrospora sphaerica from the leaf segment. Chemical and biological profiling through TLC–bioautography and hyphenated spectroscopic techniques confirmed the presence of phomalactone as an antimicrobial metabolite. Results The chemical investigation of the broth extract by bioassay-guided fractionation confirmed phomalactone as a bioactive antimicrobial secondary metabolite. The antimicrobial activity of phomalactone was found to be highest against Escherichia coli by disc diffusion assay. The MIC was found to be significant against both Escherichia coli and Xanthomonas campestris in the case of bacteria and dermatophyte Candida albicans at 150 μg/ml, respectively. Conclusions Overall, the results highlighted the antimicrobial potential of phomalactone from the endophyte Nigrospora sphaerica exhibiting a broad spectrum of antimicrobial activity against human and phytopathogenic bacteria and fungi. This work is the first report regarding the antibacterial activity of phomalactone.


Biomolecules ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 542
Author(s):  
Gustavo Penteado Battesini Carretero ◽  
Greice Kelle Viegas Saraiva ◽  
Magali Aparecida Rodrigues ◽  
Sumika Kiyota ◽  
Marcelo Porto Bemquerer ◽  
...  

In a large variety of organisms, antimicrobial peptides (AMPs) are primary defenses against pathogens. BP100 (KKLFKKILKYL-NH2), a short, synthetic, cationic AMP, is active against bacteria and displays low toxicity towards eukaryotic cells. BP100 acquires a α-helical conformation upon interaction with membranes and increases membrane permeability. Despite the volume of information available, the action mechanism of BP100, the selectivity of its biological effects, and possible applications are far from consensual. Our group synthesized a fluorescent BP100 analogue containing naphthalimide linked to its N-terminal end, NAPHT-BP100 (Naphthalimide-AAKKLFKKILKYL-NH2). The fluorescence properties of naphthalimides, especially their spectral sensitivity to microenvironment changes, are well established, and their biological activities against transformed cells and bacteria are known. Naphthalimide derived compounds are known to interact with DNA disturbing related processes as replication and transcription, and used as anticancer agents due to this property. A wide variety of techniques were used to demonstrate that NAPHT-BP100 bound to and permeabilized zwitterionic POPC and negatively charged POPC:POPG liposomes and, upon interaction, acquired a α-helical structure. Membrane surface high peptide/lipid ratios triggered complete permeabilization of the liposomes in a detergent-like manner. Membrane disruption was driven by charge neutralization, lipid aggregation, and bilayer destabilization. NAPHT-BP100 also interacted with double-stranded DNA, indicating that this peptide could also affect other cellular processes besides causing membrane destabilization. NAPHT-BP100 showed increased antibacterial and hemolytic activities, compared to BP100, and may constitute an efficient antimicrobial agent for dermatological use. By conjugating BP100 and naphthalimide DNA binding properties, NAPHT-BP100 bound to a large extent to the bacterial membrane and could more efficiently destabilize it. We also speculate that peptide could enter the bacteria cell and interact with its DNA in the cytoplasm.


2021 ◽  
Vol 62 (1) ◽  
Author(s):  
Junpeng Li ◽  
Shuping Hu ◽  
Wei Jian ◽  
Chengjian Xie ◽  
Xingyong Yang

AbstractAntimicrobial peptides (AMPs) are a class of short, usually positively charged polypeptides that exist in humans, animals, and plants. Considering the increasing number of drug-resistant pathogens, the antimicrobial activity of AMPs has attracted much attention. AMPs with broad-spectrum antimicrobial activity against many gram-positive bacteria, gram-negative bacteria, and fungi are an important defensive barrier against pathogens for many organisms. With continuing research, many other physiological functions of plant AMPs have been found in addition to their antimicrobial roles, such as regulating plant growth and development and treating many diseases with high efficacy. The potential applicability of plant AMPs in agricultural production, as food additives and disease treatments, has garnered much interest. This review focuses on the types of plant AMPs, their mechanisms of action, the parameters affecting the antimicrobial activities of AMPs, and their potential applications in agricultural production, the food industry, breeding industry, and medical field.


Molecules ◽  
2021 ◽  
Vol 26 (2) ◽  
pp. 444
Author(s):  
Motoharu Hirano ◽  
Chihiro Saito ◽  
Hidetomo Yokoo ◽  
Chihiro Goto ◽  
Ryuji Kawano ◽  
...  

Magainin 2 (Mag2), which was isolated from the skin of the African clawed frog, is a representative antimicrobial peptide (AMP) that exerts antimicrobial activity via microbial membrane disruption. It has been reported that the helicity and amphipathicity of Mag2 play important roles in its antimicrobial activity. We investigated and recently reported that 17 amino acid residues of Mag2 are required for its antimicrobial activity, and accordingly developed antimicrobial foldamers containing α,α-disubstituted amino acid residues. In this study, we further designed and synthesized a set of Mag2 derivatives bearing the hydrocarbon stapling side chain for helix stabilization. The preferred secondary structures, antimicrobial activities, and cell-membrane disruption activities of the synthesized peptides were evaluated. Our analyses revealed that hydrocarbon stapling strongly stabilized the helical structure of the peptides and enhanced their antimicrobial activity. Moreover, peptide 2 stapling between the first and fifth position from the N-terminus showed higher antimicrobial activity than that of Mag2 against both gram-positive and gram-negative bacteria without exerting significant hemolytic activity. To investigate the modes of action of tested peptides 2 and 8 in antimicrobial and hemolytic activity, electrophysiological measurements were performed.


Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3170
Author(s):  
Wafaa M. Elkady ◽  
Mariam H. Gonaid ◽  
Miriam F. Yousif ◽  
Mahmoud El-Sayed ◽  
Hind A. N. Omar

Active components from natural sources are the current focus in most pharmacological research to provide new therapeutic agents for clinical use. Essential oils from the Pinus species have been traditionally used in medicine. This study aimed to investigate the chemical profile of two Pinus species, Pinus halepensis L. and Pinus pinea Mill, from different altitudes in Libya and study the effect of environmental conditions on the biological activities of essential oils. A clevenger apparatus was used to prepare the essential oils by hydrodistillation. Analyses were done using GC/MS. Anthelmintic and antimicrobial activities were tested against the earthworm Allolobophora caliginosa, gram-positive bacteria, gram-negative bacteria, and fungi. Different chemical profiles were observed among all tested essential oils, and terpenes were the most dominant class. All studied essential oils from the Pinus species exhibited a remarkable anthelmintic activity compared to the standard piperazine citrate drug. Pinus halepensis from both altitudes showed broad-spectrum antimicrobial activity against all tested microorganisms, while Pinus pinea was effective against only Escherichia coli. From these findings, one can conclude that there are variations between studied species. The essential oil compositions are affected by environmental factors, which consequently affect the anthelmintic and antimicrobial activity.


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