scholarly journals Effects of Acyl versus Aminoacyl Conjugation on the Properties of Antimicrobial Peptides

2005 ◽  
Vol 49 (6) ◽  
pp. 2412-2420 ◽  
Author(s):  
Inna S. Radzishevsky ◽  
Shahar Rotem ◽  
Fadia Zaknoon ◽  
Leonid Gaidukov ◽  
Arie Dagan ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Self Assembly ◽  
Leishmania Major ◽  
Hydrophobic Interactions ◽  
Gradual Increase ◽  
Helical Structure ◽  
Target Cells ◽  
Human Red Blood Cells ◽  
Chain Lengths ◽  
Acyl Derivatives

ABSTRACT To investigate the importance of increased hydrophobicity at the amino end of antimicrobial peptides, a dermaseptin derivative was used as a template for a systematic acylation study. Through a gradual increase of the acyl moiety chain length, hydrophobicity was monitored and further modulated by acyl conversion to aminoacyl. The chain lengths of the acyl derivatives correlated with a gradual increase in the peptide's global hydrophobicity and stabilization of its helical structure. The effect on cytolytic properties, however, fluctuated for different cells. Whereas acylation gradually enhanced hemolysis of human red blood cells and antiprotozoan activity against Leishmania major, bacteria displayed a more complex behavior. The gram-positive organism Staphylococcus aureus was most sensitive to intermediate acyl chains, while longer acyls gradually led to a total loss of activity. All acyl derivatives were detrimental to activity against Escherichia coli, namely, but not solely, because of peptide aggregation. Although aminoacyl derivatives behaved essentially similarly to the nonaminated acyls, they displayed reduced hydrophobicity, and consequently, the long-chain acyls enhanced activity against all microorganisms (e.g., by up to 12-fold for the aminolauryl derivative) but were significantly less hemolytic than their acyl counterparts. Acylation also enhanced bactericidal kinetics and peptide resistance to plasma proteases. The similarities and differences upon acylation of MSI-78 and LL37 are presented and discussed. Overall, the data suggest an approach that can be used to enhance the potencies of acylated short antimicrobial peptides by preventing hydrophobic interactions that lead to self-assembly in solution and, thus, to inefficacy against cell wall-containing target cells.

scholarly journals The Continuing Story of Class IIa Bacteriocins

2006 ◽  
Vol 70 (2) ◽  
pp. 564-582 ◽  
Author(s):  
Djamel Drider ◽  
Gunnar Fimland ◽  
Yann Héchard ◽  
Lynn M. McMullen ◽  
Hervé Prévost
Keyword(s):  
Cell Membrane ◽  
Antimicrobial Peptides ◽  
Structure Function ◽  
Target Cell ◽  
Pathogenic Bacteria ◽  
High Efficiency ◽  
Hydrophobic Interactions ◽  
Structural Similarity ◽  
Target Cells ◽  
Dominant Group

SUMMARY Many bacteria produce antimicrobial peptides, which are also referred to as peptide bacteriocins. The class IIa bacteriocins, often designated pediocin-like bacteriocins, constitute the most dominant group of antimicrobial peptides produced by lactic acid bacteria. The bacteriocins that belong to this class are structurally related and kill target cells by membrane permeabilization. Despite their structural similarity, class IIa bacteriocins display different target cell specificities. In the search for new antibiotic substances, the class IIa bacteriocins have been identified as promising new candidates and have thus received much attention. They kill some pathogenic bacteria (e.g., Listeria) with high efficiency, and they constitute a good model system for structure-function analyses of antimicrobial peptides in general. This review focuses on class IIa bacteriocins, especially on their structure, function, mode of action, biosynthesis, bacteriocin immunity, and current food applications. The genetics and biosynthesis of class IIa bacteriocins are well understood. The bacteriocins are ribosomally synthesized with an N-terminal leader sequence, which is cleaved off upon secretion. After externalization, the class IIa bacteriocins attach to potential target cells and, through electrostatic and hydrophobic interactions, subsequently permeabilize the cell membrane of sensitive cells. Recent observations suggest that a chiral interaction and possibly the presence of a mannose permease protein on the target cell surface are required for a bacteria to be sensitive to class IIa bacteriocins. There is also substantial evidence that the C-terminal half penetrates into the target cell membrane, and it plays an important role in determining the target cell specificity of these bacteriocins. Immunity proteins protect the bacteriocin producer from the bacteriocin it secretes. The three-dimensional structures of two class IIa immunity proteins have been determined, and it has been shown that the C-terminal halves of these cytosolic four-helix bundle proteins specify which class IIa bacteriocin they protect against.

Engineering “Antimicrobial Peptides” and Other Peptides to Modulate Protein-Protein Interactions in Cancer

2020 ◽  
Vol 20 (32) ◽  
pp. 2970-2983
Author(s):  
Samuel J.S. Rubin ◽  
Nir Qvit
Keyword(s):  
Antimicrobial Peptides ◽  
Protein Interactions ◽  
Anticancer Agents ◽  
Cancer Therapeutics ◽  
Target Cells ◽  
Protein Protein Interactions ◽  
Peptide Backbone ◽  
Modified Peptides ◽  
Selective Death ◽  
Drug Leads

Antimicrobial peptides (AMPs) are a class of peptides found across a wide array of organisms that play key roles in host defense. AMPs induce selective death in target cells and orchestrate specific or nonspecific immune responses. Many AMPs exhibit native anticancer activity in addition to antibacterial activity, and others have been engineered as antineoplastic agents. We discuss the use of AMPs in the detection and treatment of cancer as well as mechanisms of AMP-induced cell death. We present key examples of cathelicidins and transferrins, which are major AMP families. Further, we discuss the critical roles of protein-protein interactions (PPIs) in cancer and how AMPs are well-suited to target PPIs based on their unique drug-like properties not exhibited by small molecules or antibodies. While peptides, including AMPs, can have limited stability and bioavailability, these issues can be overcome by peptide backbone modification or cyclization (e.g., stapling) and by the use of delivery systems such as cellpenetrating peptides (CPPs), respectively. We discuss approaches for optimizing drug properties of peptide and peptidomimetic leads (modified peptides), providing examples of promising techniques that may be applied to AMPs. These molecules represent an exciting resource as anticancer agents with unique therapeutic advantages that can target challenging mechanisms involving PPIs. Indeed, AMPs are suitable drug leads for further development of cancer therapeutics, and many studies to this end are underway.

The Investigation of the Self-Assembly of Crossed Multi-Shell Gold Nanowires

2007 ◽  
Vol 121-123 ◽  
pp. 401-406
Author(s):  
Jenn Sen Lin ◽  
Shin Pon Ju ◽  
M.H. Weng ◽  
Wen Jay Lee
Keyword(s):  
Molecular Dynamics ◽  
Circuit Design ◽  
Self Assembly ◽  
Helical Structure ◽  
The Self ◽  
Gold Nanowires ◽  
Motion Trajectory ◽  
Angular Correlation Function ◽  
Fcc Structure ◽  
Atom Motion

In this study, the molecular dynamics is employed to simulate the selfassembly of crossed gold nanowires at various temperatures. The nanowires with a multi-shell helical (HMS) structure are different from those of the bulk FCC structure. This work compares the morphology of crossed HMS nanowires with 7-1 structure after self-assembly and investigates the atom motion trajectory on the joint. The structure transform are observed from helical structure to FCC structure by angular correlation function (ACF). The results can be suggested for a nano-scale circuit design.

scholarly journals Living supramolecular polymerization of fluorinated cyclohexanes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Oleksandr Shyshov ◽  
Shyamkumar Vadakket Haridas ◽  
Luca Pesce ◽  
Haoyuan Qi ◽  
Andrea Gardin ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Self Assembly ◽  
Materials Science ◽  
Helical Structure ◽  
The Self ◽  
Supramolecular Polymers ◽  
Aliphatic Compound ◽  
Double Helical Structure ◽  
Key Driver ◽  
Supramolecular Polymerization

AbstractThe development of powerful methods for living covalent polymerization has been a key driver of progress in organic materials science. While there have been remarkable reports on living supramolecular polymerization recently, the scope of monomers is still narrow and a simple solution to the problem is elusive. Here we report a minimalistic molecular platform for living supramolecular polymerization that is based on the unique structure of all-cis 1,2,3,4,5,6-hexafluorocyclohexane, the most polar aliphatic compound reported to date. We use this large dipole moment (6.2 Debye) not only to thermodynamically drive the self-assembly of supramolecular polymers, but also to generate kinetically trapped monomeric states. Upon addition of well-defined seeds, we observed that the dormant monomers engage in a kinetically controlled supramolecular polymerization. The obtained nanofibers have an unusual double helical structure and their length can be controlled by the ratio between seeds and monomers. The successful preparation of supramolecular block copolymers demonstrates the versatility of the approach.

scholarly journals Tubular Assembly Formation Induced by Leucine Alignment along the Hydrophobic Helix of Amphiphilic Polypeptides

2021 ◽  
Vol 22 (21) ◽  
pp. 12075
Author(s):  
Mohammed A. Abosheasha ◽  
Toru Itagaki ◽  
Yoshihiro Ito ◽  
Motoki Ueda
Keyword(s):  
Double Layer ◽  
Self Assembly ◽  
Helical Structure ◽  
Tube Formation ◽  
Rolled Sheet ◽  
Α Helix ◽  
Necessary And Sufficient ◽  
Hydrophobic Helix ◽  
Nanotube Dispersion ◽  
Spherical Vesicles

The introduction of α-helical structure with a specific helix–helix interaction into an amphipathic molecule enables the determination of the molecular packing in the assembly and the morphological control of peptide assemblies. We previously reported that the amphiphilic polypeptide SL12 with a polysarcosine (PSar) hydrophilic chain and hydrophobic α-helix (l-Leu-Aib)6 involving the LxxxLxxxL sequence, which induces homo-dimerization due to the concave–convex interaction, formed a nanotube with a uniform 80 nm diameter. In this study, we investigated the importance of the LxxxLxxxL sequence for tube formation by comparing amphiphilic polypeptide SL4A4L4 with hydrophobic α-helix (l-Leu-Aib)2-(l-Ala-Aib)2-(l-Leu-Aib)2 and SL12. SL4A4L4 formed spherical vesicles and micelles. The effect of the LxxxLxxxL sequence elongation on tube formation was demonstrated by studying assemblies of PSar-b-(l-Ala-Aib)-(l-Leu-Aib)6-(l-Ala-Aib) (SA2L12A2) and PSar-b-(l-Leu-Aib)8 (SL16). SA2L12A2 formed nanotubes with a uniform 123 nm diameter, while SL16 assembled into vesicles. These results showed that LxxxLxxxL is a necessary and sufficient sequence for the self-assembly of nanotubes. Furthermore, we fabricated a double-layer nanotube by combining two kinds of nanotubes with 80 and 120 nm diameters—SL12 and SA2L12A2. When SA2L12A2 self-assembled in SL12 nanotube dispersion, SA2L12A2 initially formed a rolled sheet, the sheet then wrapped the SL12 nanotube, and a double-layer nanotube was obtained.

scholarly journals Phlebotomus papatasi Antimicrobial Peptides in Larvae and Females and a Gut-Specific Defensin Upregulated by Leishmania major Infection

2021 ◽  
Vol 9 (11) ◽  
pp. 2307
Author(s):  
Barbora Kykalová ◽  
Lucie Tichá ◽  
Petr Volf ◽  
Erich Loza Telleria
Keyword(s):  
Gene Expression ◽  
Antimicrobial Peptides ◽  
Leishmania Major ◽  
Larval Instar ◽  
Gut Bacteria ◽  
Sand Fly ◽  
Control Group ◽  
Phlebotomus Papatasi ◽  
Major Infection ◽  
Defensin Gene

Phlebotomus papatasi is the vector of Leishmania major, causing cutaneous leishmaniasis in the Old World. We investigated whether P. papatasi immunity genes were expressed toward L. major, commensal gut microbes, or a combination of both. We focused on sand fly transcription factors dorsal and relish and antimicrobial peptides (AMPs) attacin and defensin and assessed their relative gene expression by qPCR. Sand fly larvae were fed food with different bacterial loads. Relish and AMPs gene expressions were higher in L3 and early L4 larval instars, while bacteria 16S rRNA increased in late L4 larval instar, all fed rich-microbe food compared to the control group fed autoclaved food. Sand fly females were treated with an antibiotic cocktail to deplete gut bacteria and were experimentally infected by Leishmania. Compared to non-infected females, dorsal and defensin were upregulated at early and late infection stages, respectively. An earlier increase of defensin was observed in infected females when bacteria recolonized the gut after the removal of antibiotics. Interestingly, this defensin gene expression occurred specifically in midguts but not in other tissues of females and larvae. A gut-specific defensin gene upregulated by L. major infection, in combination with gut-bacteria, is a promising molecular target for parasite control strategies.

scholarly journals Structural control for the coordinated assembly into functional pathogenic type-3 secretion systems

2019 ◽  
Author(s):  
Nikolaus Goessweiner-Mohr ◽  
Vadim Kotov ◽  
Matthias J. Brunner ◽  
Julia Mayr ◽  
Jiri Wald ◽  
...  
Keyword(s):  
Self Assembly ◽  
Structural Control ◽  
Helical Structure ◽  
Structural Basis ◽  
Protein Chain ◽  
Assembly Process ◽  
Secretion Systems ◽  
Ring Assembly ◽  
Serovar Typhimurium ◽  
Type 3

AbstractFunctional injectisomes of the type-3 secretion system assemble into highly defined and stoichiometric bacterial molecular machines essential for infecting human and other eukaryotic cells. However, the mechanism that governs the regulated step-wise assembly process from the nucleation-phase, to ring-assembly, and the filamentous phase into a membrane embedded needle complex is unclear. We here report that the formation of a megadalton-sized needle complexes from Salmonella enterica serovar Typhimurium (SPI-1, Salmonella pathogenicity island-1) with proper stoichiometries is highly structurally controlled competing against the self-assembly propensity of injectisome components, leading to a highly unusual structurally-pleiotropic phenotype. The structure of the entire needle complex from pathogenic injectisomes was solved by cryo electron microscopy, focused refinements (2.5-4 Å) and co-variation analysis revealing an overall asymmetric arrangement containing cyclic, helical, and asymmetric sub-structures. The centrally located export apparatus assembles into a conical, pseudo-helical structure and provides a structural template that guides the formation of a 24-mer cyclic, surrounding ring, which then serves as a docking interface comprising three different conformations for sixteen N-terminal InvG subunits of the outer secretin ring. Unexpectedly, the secretin ring excludes the 16th protein chain at the C-terminal outer ring, resulting in a pleiotropic 16/15-mer ring and consequently to an overall 24:16/15 basal body structure. Finally, we report how the transition from the pseudo-helical export apparatus into the helical filament is structurally resolved to generate the protein secretion channel, which provides the structural basis to restrict access of unfolded effector substrates. These results highlight the diverse molecular signatures required for a highly coordinated assembly process and provide the molecular basis for understanding triggering and transport of unfolded proteins through injectisomes.

scholarly journals Rules for the self-assembly of ESCRT-III on endosomes

2021 ◽  
Author(s):  
Simon Sprenger ◽  
Simona M. Migliano ◽  
Florian Oleschko ◽  
Marvin Kobald ◽  
Michael Hess ◽  
...  
Keyword(s):  
Self Assembly ◽  
Hydrophobic Interactions ◽  
The Self ◽  
Amino Acid Residues ◽  
Lateral Expansion ◽  
Endosomal Sorting ◽  
Aaa Atpase ◽  
Charged Amino Acids ◽  
Membrane Budding ◽  
Positively Charged

ABSTRACTThe endosomal sorting complexes required for transport (ESCRT) mediate various membrane remodeling processes in cells by mechanism that are incompletely understood. Here we combined genetic experiments in budding yeast with site-specific cross-linking to identify rules that govern the self-assembly of individual ESCRT-III proteins into functional ESCRT-III complexes on endosomes. Together with current structural models of ESCRT-III, our findings suggest that, once nucleated, the growing Snf7 protofilament seeds the lateral co-assembly of a Vps24 - Vps2 heterofilament. Both Vps24 and Vps2 use positively charged amino acid residues in their helices α1 to interact with negatively charged amino acids in helix α4 of Snf7 subunits of the protofilament. In the Vps24 - Vps2 heterofilament, the two subunits alternate and interact with each other using hydrophobic interactions between helices α2/α3. The co-assembly of the Vps24 - Vps2 heterofilament restricts the lateral expansion of Snf7 protofilaments and leads the immediate recruitment of the AAA-ATPase Vps4. This self-assembly process of three ESCRT-III subunits results in the formation of a Snf7 protofilament and the co-assembly of a Vps24 - Vps2 heterofilament. This sets the stage for Vps4 recruitment and the subsequent ATP-driven dynamic self-organization of ESCRT-III / Vps4 assemblies and the ensuing membrane budding and scission events.

Self-assembly of gold nanoparticles in a block copolymer aggregate template driven by hydrophobic interactions

2019 ◽  
Vol 10 (46) ◽  
pp. 6269-6277
Author(s):  
Jong Dae Jang ◽  
Sang-Woo Jeon ◽  
Young-Jin Yoon ◽  
Joona Bang ◽  
Young Soo Han ◽  
...  
Keyword(s):  
Gold Nanoparticles ◽  
Block Copolymer ◽  
Self Assembly ◽  
Hydrophobic Interactions ◽  
Self Assembled

We report various self-assembled structures of gold nanoparticles in a block copolymer aggregate template, which are easily driven by hydrophobic interactions.

scholarly journals Effect of the Hydrophilic-Hydrophobic Balance of Antigen-Loaded Peptide Nanofibers on Their Cellular Uptake, Cellular Toxicity, and Immune Stimulatory Properties

2019 ◽  
Vol 20 (15) ◽  
pp. 3781 ◽  
Author(s):  
Tomonori Waku ◽  
Saki Nishigaki ◽  
Yuichi Kitagawa ◽  
Sayaka Koeda ◽  
Kazufumi Kawabata ◽  
...  
Keyword(s):  
Cellular Uptake ◽  
Self Assembly ◽  
Sheet Forming ◽  
Design Guidelines ◽  
Cellular Interactions ◽  
Antigenic Peptides ◽  
Peptide Nanofibers ◽  
Dc Line ◽  
Chain Lengths ◽  
Β Sheet

Recently, nanofibers (NFs) formed from antigenic peptides conjugated to β-sheet-forming peptides have attracted much attention as a new generation of vaccines. However, studies describing how the hydrophilic-hydrophobic balance of NF components affects cellular interactions of NFs are limited. In this report, three different NFs were prepared by self-assembly of β-sheet-forming peptides conjugated with model antigenic peptides (SIINFEKL) from ovalbumin and hydrophilic oligo-ethylene glycol (EG) of differing chain lengths (6-, 12- and 24-mer) to investigate the effect of EG length of antigen-loaded NFs on their cellular uptake, cytotoxicity, and dendritic cell (DC)-stimulation ability. We used an immortal DC line, termed JAWS II, derived from bone marrow-derived DCs of a C57BL/6 p53-knockout mouse. The uptake of NFs, consisting of the EG 12-mer by DCs, was the most effective and activated DC without exhibiting significant cytotoxicity. Increasing the EG chain length significantly reduced cellular entry and DC activation by NFs. Conversely, shortening the EG chain enhanced DC activation but increased toxicity and impaired water-dispersibility, resulting in low cellular uptake. These results show that the interaction of antigen-loaded NFs with cells can be tuned by the EG length, which provides useful design guidelines for the development of effective NF-based vaccines.

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