Mechanistic Studies of Antimicrobial Peptides in Lipid Membranes (original) (raw)
Related papers
Antimicrobial peptides: natural templates for synthetic membrane-active compounds
The innate immunity of multicellular organisms relies in large part on the action of antimicrobial peptides (AMPs) to resist microbial invasion. Crafted by evolution into an extremely diversified array of sequences and folds, AMPs do share a common amphiphilic 3-Darrangement.This feature is directly linked with a common mechanism of action that predominantly (although not exclusively) develops upon interaction of peptides with cell membranes of target cells. This minireview reports on current understanding of the modes of interaction of AMPs with biological and model membranes, especially focusing on recent insights into the folding and oligomerization requirements of peptides to bind and insert into lipid membranes and exert their antibiotic effects. Given the potential of AMPs to be developed into a new class of anti-infective agents, emphasis is placed on how the information on peptidemembrane interactions could direct the design and selection of improved biomimetic synthetic peptides with antibiotic properties
Chemistry – A European Journal, 2020
In the quest for new antibiotics, two novel engineered cationic antimicrobial peptides (eCAPs) have been rationally designed. WLBU2 and D8 (all 8 valines are the d‐enantiomer) efficiently kill both Gram‐negative and ‐positive bacteria, but WLBU2 is toxic and D8 nontoxic to eukaryotic cells. We explore protein secondary structure, location of peptides in six lipid model membranes, changes in membrane structure and pore evidence. We suggest that protein secondary structure is not a critical determinant of bactericidal activity, but that membrane thinning and dual location of WLBU2 and D8 in the membrane headgroup and hydrocarbon region may be important. While neither peptide thins the Gram‐negative lipopolysaccharide outer membrane model, both locate deep into its hydrocarbon region where they are primed for self‐promoted uptake into the periplasm. The partially α‐helical secondary structure of WLBU2 in a red blood cell (RBC) membrane model containing 50 % cholesterol, could play a ro...
Interaction of an artificial antimicrobial peptide with lipid membranes
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2009
Antimicrobial peptides constitute an important part of the innate immune defense and are promising new candidates for antibiotics. Naturally occurring antimicrobial peptides often possess hemolytic activity and are not suitable as drugs. Therefore, a range of new synthetic antimicrobial peptides have been developed in recent years with promising properties. But their mechanism of action is in most cases not fully understood. One of these peptides, called V4, is a cyclized 19 amino acid peptide whose amino acid sequence has been modeled upon the hydrophobic/cationic binding pattern found in Factor C of the horseshoe crab (Carcinoscorpius rotundicauda). In this work we used a combination of biophysical techniques to elucidate the mechanism of action of V4. Langmuir-Blodgett trough, atomic force microscopy, Fluorescence Correlation Spectroscopy, Dual Polarization Interference, and confocal microscopy experiments show how the hydrophobic and cationic properties of V4 lead to a) selective binding of the peptide to anionic lipids (POPG) versus zwitterionic lipids (POPC), b) aggregation of vesicles, and above a certain concentration threshold to c) integration of the peptide into the bilayer and finally d) to the disruption of the bilayer structure. The understanding of the mechanism of action of this peptide in relation to the properties of its constituent amino acids is a first step in designing better peptides in the future.
Biochemical and Biophysical Research Communications, 2008
In this study, we employed electrophysiology experiments carried out at the single-molecule level to study the mechanism of action of the HPA3 peptide, an analogue of the linear antimicrobial peptide, HP(2-20), isolated from the N-terminal region of the Helicobacter pylori ribosomal protein. Amplitude analysis of currents fluctuations induced by HPA3 peptide at various potentials in zwitterionic lipid membranes reveal the existence of reproducible conductive states in the stochastic behavior of such events, which directly supports the existence of transmembrane pores induced the peptide. From our data recorded both at the single-pore and macroscopic levels, we propose that the HPA3 pore formation is electrophoretically facilitated by trans-negative transmembrane potentials, and HPA3 peptides translocate into the trans monolayers after forming the pores. We present evidence according to which the decrease in the membrane dipole potential of a reconstituted lipid membranes leads to an augmentation of the membrane activity of HPA3 peptides, and propose that a lower electric dipole field of the interfacial region of the membrane caused by phloretin facilitates the surface-bound HPA3 peptides to break free from one leaflet of the membrane, insert into the membrane and contribute to pore formation spanning the entire thickness of the membrane.
Lipid II as a Target for Novel Antibiotics: Structural and Molecular Dynamics Studies
Russian Journal of Bioorganic Chemistry, 2018
⎯The growing problem of antibiotic resistance in medicine is focusing attention on antimicrobial compounds targeting non-protein molecules, which have more conserved structures compared to proteins or peptides. One of the most promising and studied targets is lipid II-the bacterial cell wall biosynthetic pathway principal compound. Lipid II is unique for the bacterial membrane only and has a conserved chemical structure. There are several classes of natural antibiotics targeting lipid II, some of which block peptidoglycan synthesis by formation of a strong complex with lipid II; others have an additional bactericidal mechanism involving disruption of the membrane integrity. This review examines the prospects of using such antibacterial substances as new drugs to combat antibiotic-resistant pathogens. The main emphasis is on the studies of the membrane-embedded lipid II structure and how water-soluble antibiotics recognize its molecular structure, as well as on computer modeling of their interaction.
Antimicrobial Peptides Induce Growth of Phosphatidylglycerol Domains in a Model Bacterial Membrane
2010
We performed microsecond long coarse-grained molecular dynamics simulations to elucidate the lateral structure and domain dynamics of a phosphatidylethanolamine (PE)/phosphatidylglycerol (PG) mixed bilayer (7/3), mimicking the inner membrane of gram-negative bacteria. Specifically, we address the effect of surface bound antimicrobial peptides (AMPs) on the lateral organization of the membrane. We find that, in the absence of the peptides, the minor PG fraction only forms small clusters, but that these clusters grow in size upon binding of the cationic AMPs. The presence of AMPs systematically affects the dynamics and induces long-range order in the structure of PG domains, stabilizing the separation between the two lipid fractions. Our results help in understanding the initial stages of destabilization of cytoplasmic bacterial membranes below the critical peptide concentration necessary for disruption, and provide a possible explanation for the multimodal character of AMP activity.
Antimicrobial Peptide Structure and Mechanism of Action: A Focus on the Role of Membrane Structure
Antimicrobial peptides (AMPs) are showing increasing promise as potential candidate antibacterial drugs in the face of the rapidly emerging bacterial resistance to conventional antibiotics in recent years. The target of these peptides is the microbial membrane and there are numerous models to explain their mechanism of action ranging from pore formation to general membrane disruption. The interaction between the AMP and the target membrane is critical to the specificity and activity of these peptides. However, a precise understanding of the relationship between antimicrobial peptide structure and their cytolytic function in a range of organisms is still lacking. This is a result of the complex nature of the interactions of AMPs with the cell membrane, the mechanism of which can vary considerably between different classes of antimicrobia peptides. A wide range of biophysical techniques have been used to study the influence of a number of peptide and membrane properties on the cytolytic activity of these peptides in model membrane systems. Central to characterisation of this interaction is a quantitative analysis of the binding of peptide to the membrane and the coherent dynamic changes in membrane structure. Recently, dual polarization interferometry has been used to perform an in depth analysis of antimicrobial peptide induced membrane perturbation and with new mass-structure co-fitting kinetic analysis have allowed a real-time label free analysis of binding affinity and kinetics. We review these studies which describe multi-step mechanisms which are adopted by various AMPs in nature and may advance our approach to the development of a new generation of effective antimicrobial therapeutics.
Colloids and surfaces. B, Biointerfaces, 2017
Antimicrobial peptides (AMPs) are small cationic molecules that display antimicrobial activity against a wide range of bacteria, fungi and viruses. For an AMP to be considered as a therapeutic option, it must have not only potent antibacterial properties but also low hemolytic and cytotoxic activities [1]. Even though many studies have been conducted in order to correlate the antimicrobial activity with affinity toward model lipid membranes, the use of these membranes to explain cytotoxic effects (especially hemolysis) has been less explored. In this context, we studied lipid selectivity in two related novel AMPs, peptide 6 (P6) and peptide 6.2 (P6.2). Each peptide was designed from a previously reported AMP, and specific amino acid replacements were performed in an attempt to shift their hydrophobic moment or net charge. P6 showed no antimicrobial activity and high hemolytic activity, and P6.2 exhibited good antibacterial and low hemolytic activity. Using both peptides as a model w...
European Journal of Biochemistry, 1997
The interaction of PGLa (peptidyl-glycylleucine-carboxyamide), a 21-amino-acid residue cationic peptide, isolated from the skin of the South African clawed frog, Xenopus luevis, with model membrane systems was investigated. Our studies focussed on the importance of the difference in the phospholipid composition of bacterial and erythrocyte membranes. This is of particular interest to gain information on the specificity of membranolysis exhibited by this peptide against bacteria but not against erythrocytes. In phosphate buffer at physiological pH, as well as in the presence of the zwitterionic phosphatidylcholine and sphingomyelin, the peptide had a random structure but it adopted an a-helical conformation in the presence of negatively charged lipids. Furthermore, calorimetric experiments showed that PGLa had no effects on the thermotropic phase behavior of liposomes composed of the choline phosphatides, while separation of a distinct peptide-rich domain was observed for phosphatidylglycerol liposomes. In addition to the main transition of pure 1,2-dipalmitoylglycerophosphoglycerol at 40°C a second transition owing to the peptide-perturbed lipid domains was found at 41 "C. This conclusion is supported by X-ray diffraction experiments which indicated that PGLa penetrates into the hydrophobic core of the bilayer inducing an untilting of the hydrocarbon chains as observed in the gel phase of the pure lipid. These results demonstrate that this antibacterial peptide specifically interacts with negatively charged lipid membranes, which are characteristic of bacterial membranes. This can be explained based on the structural features of PGLa.
Antimicrobial activity and membrane selective interactions of a synthetic lipopeptide MSI-843
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2005
Lipopeptide MSI-843 consisting of the nonstandard amino acid ornithine (Oct-OOLLOOLOOL-NH 2) was designed with an objective towards generating non-lytic short antimicrobial peptides, which can have significant pharmaceutical applications. Octanoic acid was coupled to the N-terminus of the peptide to increase the overall hydrophobicity of the peptide. MSI-843 shows activity against bacteria and fungi at micromolar concentrations. It permeabilizes the outer membrane of Gramnegative bacterium and a model membrane mimicking bacterial inner membrane. Circular dichroism investigations demonstrate that the peptide adopts α-helical conformation upon binding to lipid membranes. Isothermal titration calorimetry studies suggest that the peptide binding to membranes results in exothermic heat of reaction, which arises from helix formation and membrane insertion of the peptide. 2 H NMR of deuterated-POPC multilamellar vesicles shows the peptide-induced disorder in the hydrophobic core of bilayers. 31 P NMR data indicate changes in the lipid head group orientation of POPC, POPG and Escherichia coli total lipid bilayers upon peptide binding. Results from 31 P NMR and dye leakage experiments suggest that the peptide selectively interacts with anionic bilayers at low concentrations (up to 5 mol%). Differential scanning calorimetry experiments on DiPOPE bilayers and 31 P NMR data from E. coli total lipid multilamellar vesicles indicate that MSI-843 increases the fluid lamellar to inverted hexagonal phase transition temperature of bilayers by inducing positive curvature strain. Combination of all these data suggests the formation of a lipid-peptide complex resulting in a transient pore as a plausible mechanism for the membrane permeabilization and antimicrobial activity of the lipopeptide MSI-843.