The role of hydrophobic patches of de novo designed MSI-78 and VG16KRKP antimicrobial peptides on fragmenting model bilayer membranes.

Antimicrobial peptides (AMPs) with cell membrane lysing capability are considered potential candidates for the development of the next generation of antibiotics. Designing novel AMPs requires an in-depth understanding of the mechanism of action of the peptides. In this work, we used various biophysical techniques including P solid-state NMR to examine the interaction of model membranes with amphipathic de novo-designed peptides.

Structural insights into the interaction of antifungal peptides and ergosterol containing fungal membrane.

The treatment of invasive drug-resistant and potentially life-threatening fungal infections is limited to few therapeutic options that are usually associated with severe side effects. The development of new effective antimycotics with a more tolerable side effect profile is therefore of utmost clinical importance. Here, we used a combination of complementary in vitro assays and structural analytical methods to analyze the interaction of the de novo antimicrobial peptide VG16KRKP with the sterol moieties of biological cell membranes.

A rationally designed synthetic antimicrobial peptide against Pseudomonas-associated corneal keratitis: Structure-function correlation.

Contact lens wearers are at an increased risk of developing Pseudomonas-associated corneal keratitis, which can lead to a host of serious ocular complications. Despite the use of topical antibiotics, ocular infections remain a major clinical problem, and a strategy to avoid Pseudomonas-associated microbial keratitis is urgently required. The hybrid peptide VR18 (VARGWGRKCPLFGKNKSR) was designed to have enhanced antimicrobial properties in the fight against Pseudomonas-induced microbial keratitis, including contact lens-related keratitis.

Comparison of Synthetic Neuronal Model Membrane Mimics in Amyloid Aggregation at Atomic Resolution.

Alzheimer's disease (AD) is a severe neurodegenerative disorder caused by abnormal accumulation of toxic amyloid plaques of the amyloid-beta (Aβ) or the tau proteins in the brain. The plaque deposition leading to the collapse of the cellular integrity is responsible for a myriad of surface phenomena acting at the neuronal lipid interface. Recent years have witnessed dysfunction of the blood-brain barriers (BBB) associated with AD.

Magnetic Alignment of Polymer Nanodiscs Probed by Solid-State NMR Spectroscopy.

The ability of amphipathic polymers to self-assemble with lipids and form nanodiscs has been a boon for the field of functional reconstitution of membrane proteins. In a field dominated by detergent micelles, a unique feature of polymer nanodiscs is their much-desired ability to align in the presence of an external magnetic field. Magnetic alignment facilitates the application of solid-state nuclear magnetic resonance (NMR) spectroscopy and aids in the measurement of residual dipolar couplings via well-established solution NMR spectroscopy.

Structural insights into the combinatorial effects of antimicrobial peptides reveal a role of aromatic-aromatic interactions in antibacterial synergism.

The recent development of plants that overexpress antimicrobial peptides (AMPs) provides opportunities for controlling plant diseases. Because plants employ a broad-spectrum antimicrobial defense, including those based on AMPs, transgenic modification for AMP overexpression represents a potential way to utilize a defense system already present in plants. Herein, using an array of techniques and approaches, we report on VG16KRKP and KYE28, two antimicrobial peptides, which in combination exhibit synergistic antimicrobial effects against plant pathogens and are resistant against plant proteases.

Role of non-electrostatic forces in antimicrobial potency of a dengue-virus derived fusion peptide VG16KRKP: Mechanistic insight into the interfacial peptide-lipid interactions.

Cationic antimicrobial peptides (AMPs) are emerging as effective alternatives to conventional therapeutics that are used against the ever-rising number of multidrug-resistant microbial strains. Most studies established the peptide's amphipathicity and electrostatic interaction with the membrane as the basis for their antimicrobial effect. However, the interplay between the stoichiometric ratio of lipids, local geometry, diverse physicochemical properties of the host membranes and antimicrobial peptide efficacy is still poorly understood.

A blend of two resveratrol derivatives abolishes hIAPP amyloid growth and membrane damage.

Type II diabetes mellitus (T2DM) is characterized by the presence of amyloid deposits of the human islet amyloid polypeptide (hIAPP) in pancreatic β-cells. A wealth of data supports the hypothesis that hIAPP's toxicity is related to an abnormal interaction of amyloids with islet cell membranes. Thus, many studies aimed at finding effective therapies for T2DM focus on the design of molecules that are able to inhibit hIAPP's amyloid growth and the related membrane damage as well.

Insulin-eukaryotic model membrane interaction: Mechanistic insight of insulin fibrillation and membrane disruption.

Injection of exogenous insulin in the subcutaneous mass has been a proven therapy for type II diabetes. However, chronic administration of insulin often develops local amyloidosis at the injection site, pathologically known as "Insulin Ball". This reduces the insulin bioavailability and exacerbates the disease pathology.

Detergent-type membrane fragmentation by MSI-78, MSI-367, MSI-594, and MSI-843 antimicrobial peptides and inhibition by cholesterol: a solid-state nuclear magnetic resonance study.

Multidrug resistance against the existing antibiotics is becoming a global threat, and any potential drug that can be designed using cationic antimicrobial peptides (AMP) could be an alternate solution to alleviate this existing problem. The mechanism of action of killing bacteria by an AMP differs drastically in comparison to that of small molecule antibiotics. The main target of AMPs is to interact with the lipid bilayer of the cell membrane and disrupt it to kill bacteria.

Temperature-resistant bicelles for structural studies by solid-state NMR spectroscopy.

Three-dimensional structure determination of membrane proteins is important to fully understand their biological functions. However, obtaining a high-resolution structure has been a major challenge mainly due to the difficulties in retaining the native folding and function of membrane proteins outside of the cellular membrane environment. These challenges are acute if the protein contains a large soluble domain, as it needs bulk water unlike the transmembrane domains of an integral membrane protein.

Lipid composition-dependent membrane fragmentation and pore-forming mechanisms of membrane disruption by pexiganan (MSI-78).

The potency and selectivity of many antimicrobial peptides (AMPs) are correlated with their ability to interact with and disrupt the bacterial cell membrane. In vitro experiments using model membranes have been used to determine the mechanism of membrane disruption of AMPs. Because the mechanism of action of an AMP depends on the ability of the model membrane to accurately mimic the cell membrane, it is important to understand the effect of membrane composition.

Phosphatidylethanolamine enhances amyloid fiber-dependent membrane fragmentation.

The toxicity of amyloid-forming peptides has been hypothesized to reside in the ability of protein oligomers to interact with and disrupt the cell membrane. Much of the evidence for this hypothesis comes from in vitro experiments using model membranes. However, the accuracy of this approach depends on the ability of the model membrane to accurately mimic the cell membrane.

Two-step mechanism of membrane disruption by Aβ through membrane fragmentation and pore formation.

Disruption of cell membranes by Aβ is believed to be one of the key components of Aβ toxicity. However, the mechanism by which this occurs is not fully understood. Here, we demonstrate that membrane disruption by Aβ occurs by a two-step process, with the initial formation of ion-selective pores followed by nonspecific fragmentation of the lipid membrane during amyloid fiber formation.

Comparison between clinical disabilities and electrophysiological values in Charcot-Marie-Tooth 1A patients with PMP22 duplication.

Background And Purpose: Charcot-Marie-Tooth disease (CMT) type 1A (CMT1A) is the demyelinating form of CMT that is significantly associated with PMP22 duplication. Some studies have found that the disease-related disabilities of these patients are correlated with their compound muscle action potentials (CMAPs), while others have suggested that they are related to the nerve conduction velocities. In the present study, we investigated the correlations between the disease-related disabilities and the electrophysiological values in a large cohort of Korean CMT1A patients.

Role of cationic group structure in membrane binding and disruption by amphiphilic copolymers.

Cationic, amphiphilic polymers are currently being used as antimicrobial agents that disrupt biomembranes, although their mechanisms remain poorly understood. Herein, membrane association and disruption by amphiphilic polymers bearing primary, tertiary, or quaternary ammonium salt groups reveal the role of cationic group structure in the polymer-membrane interaction. The dissociation constants of polymers to liposomes of POPC were obtained by a fluorometric assay, exploiting the environmental sensitivity of dansyl moieties in the polymer end groups.

Limiting an antimicrobial peptide to the lipid-water interface enhances its bacterial membrane selectivity: a case study of MSI-367.

In a minimalist design approach, a synthetic peptide MSI-367 [(KFAKKFA)(3)-NH(2)] was designed and synthesized with the objective of generating cell-selective nonlytic peptides, which have a significant bearing on cell targeting. The peptide exhibited potent activity against both bacteria and fungi, but no toxicity to human cells at micromolar concentrations. Bacterial versus human cell membrane selectivity of the peptide was determined via membrane permeabilization assays.

An efficient method for the expression and reconstitution of thermostable Mn/Fe superoxide dismutase from Aeropyrum pernix K1.

The gene APE0743 encoding the superoxide dismutase (ApSOD) of a hyperthermophilic archaeon Aeropyrum pernix K1 was cloned and over-expressed as a GST fusion protein at a high level in Escherichia coli. The expressed protein was simply purified by the process of glutathione affinity chromatography and thrombin treatment. The ApSOD was a homodimer of 25 kDa subunits and a cambialistic SOD which was active with either Fe(II) or Mn(II) as a cofactor.

Cholesterol reduces pardaxin's dynamics-a barrel-stave mechanism of membrane disruption investigated by solid-state NMR.

While high-resolution 3D structures reveal the locations of all atoms in a molecule, it is the dynamics that correlates the structure with the function of a biological molecule. The complete characterization of dynamics of a membrane protein is in general complex. In this study, we report the influence of dynamics on the channel-forming function of pardaxin using chemical shifts and dipolar couplings measured from 2D broadband-PISEMA experiments on mechanically aligned phospholipids bilayers.

Determining the effects of lipophilic drugs on membrane structure by solid-state NMR spectroscopy: the case of the antioxidant curcumin.

Curcumin is the active ingredient of turmeric powder, a natural spice used for generations in traditional medicines. Curcumin's broad spectrum of antioxidant, anticarcinogenic, antimutagenic, and anti-inflammatory properties makes it particularly interesting for the development of pharmaceutical compounds. Because of curcumin's various effects on the function of numerous unrelated membrane proteins, it has been suggested that it affects the properties of the bilayer itself.

Solid-state NMR and molecular dynamics simulations reveal the oligomeric ion-channels of TM2-GABA(A) stabilized by intermolecular hydrogen bonding.

The second transmembrane (TM2) domain of GABA(A) receptor forms the inner-lining surface of chloride ion-channel and plays important roles in the function of the receptor protein. In this study, we report the first structure of TM2 in lipid bilayers determined using solid-state NMR and MD simulations. The interatomic (13)C-(15)N distances measured from REDOR magic angle spinning experiments on multilamellar vesicles, containing a TM2 peptide site specifically labeled with (13)C' and (15)N isotopes, were used to determine the secondary structure of the peptide.

Freezing point depression of water in phospholipid membranes: a solid-state NMR study.

Lipid-water interaction plays an important role in the properties of lipid bilayers, cryoprotectants, and membrane-associated peptides and proteins. The temperature at which water bound to lipid bilayers freezes is lower than that of free water. Here, we report a solid-state NMR investigation on the freezing point depression of water in phospholipid bilayers in the presence and absence of cholesterol.

Nitrogen-14 solid-state NMR spectroscopy of aligned phospholipid bilayers to probe peptide-lipid interaction and oligomerization of membrane associated peptides.

Characterization of the oligomerization of membrane-associated peptides is important to understand the folding and function of biomolecules like antimicrobial peptides, fusion peptides, amyloid peptides, toxins, and ion channels. However, this has been considered to be very difficult, because the amphipathic properties of the constituents of the cell membrane pose tremendous challenges to most commonly used biophysical techniques. In this study, we present the application of a simple (14)N solid-state NMR spectroscopy of aligned model membranes containing a phosphatidyl choline lipid to investigate the oligomerization of membrane-associated peptides.

Structure, topology, and tilt of cell-signaling peptides containing nuclear localization sequences in membrane bilayers determined by solid-state NMR and molecular dynamics simulation studies.

Cell-signaling peptides have been extensively used to transport functional molecules across the plasma membrane into living cells. These peptides consist of a hydrophobic sequence and a cationic nuclear localization sequence (NLS). It has been assumed that the hydrophobic region penetrates the hydrophobic lipid bilayer and delivers the NLS inside the cell.

Solid-state NMR investigation of the membrane-disrupting mechanism of antimicrobial peptides MSI-78 and MSI-594 derived from magainin 2 and melittin.

The mechanism of membrane interaction of two amphipathic antimicrobial peptides, MSI-78 and MSI-594, derived from magainin-2 and melittin, is presented. Both the peptides show excellent antimicrobial activity. The 8-anilinonaphthalene-1-sulfonic acid uptake experiment using Escherichia coli cells suggests that the outer membrane permeabilization is mainly due to electrostatic interactions.