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Antimicrobial Peptides: Structure and Mechanism of Biological Activity 3.0

A special issue of International Journal of Molecular Sciences (ISSN 1422-0067). This special issue belongs to the section "Molecular Microbiology".

Deadline for manuscript submissions: 30 June 2024 | Viewed by 4522

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Guest Editor
Departamento de Nutrición y Ciencia de los Alimentos (NUTRYCIAL), Sección Departamental de Nutrición y Ciencia de los Alimentos (SD-NUTRYCIAL), Facultad de Veterinaria, Universidad Complutense de Madrid (UCM), Avenida Puerta de Hierro, s/n, 28040 Madrid, Spain
Interests: microbiology; antimicrobial peptides; synthetic biology; biotechnology; bacteriocins

Special Issue Information

Dear Colleagues,

Since the early 1960s, the resistance of microbes against antibiotics has been recognized as a potential global health issue. This issue is now critical due to the reemergence of several infectious diseases of microbial origin and prevalence of multidrug-resistant microbes. Antimicrobial peptides (AMPs) have offered a good potential for novel drugs against drug-resistant microbial organisms, and extensive research has been dedicated to the discovery, characterization, de novo design, and assessment of the antimicrobial activity of these peptides since the late 1980s. So far, more than 3000 AMPs have been characterized and documented. These peptides have diverse natural origins and are found in unicellular organisms (bacteria, archaea, protists, and fungi), plants, and animals. Close to 75% of AMPs are found in animals, ~11% in plants, and about the same number in bacteria. Based on the sequences of these naturally found peptides, new chemically modified synthetic peptides have been designed to enhance or modify the biological activity of the original peptides. AMPs are also diverse in their biological activities and can be multifunctional. In addition to their antimicrobial activity, AMPs can have other biological functions, such as antioxidant, anticancer, antimalarial, chemotactic (modulation of immune systems), and wound healing. The diversity of AMPs expands to their physicochemical properties, structure, and mechanism of biological activity, which are the foci of this Special Issue. Most, but not all, AMPs are positively charged, and negatively and neutrally charged peptides can also be found. AMPs have different structures (α-helix, β-sheet, turn, or nonspecific interconvertible dynamic structures), overall hydrophobicity and amphipathicity, and can be linear, cyclic, or a combination of both. Many AMPs interact with the lipid membranes of the microbial/nonmicrobial cells and destroy these cells by disrupting the osmotic balance across the membrane. Some AMPs can pass across cell membranes and interact with intracellular targets such as organelle membranes, receptor proteins, or DNA. In the late 1980s and during the 1990s, several models were proposed for the mechanism of interaction of AMPs with model cell membranes, which generally include self-association of peptides and/or peptide–lipid association from specific well-defined pores or to induce nonspecific leakage. The mechanisms of translocation of AMPs through cell membranes and their successive interaction with intracellular molecules are less investigated. Understanding and visualizing the structural dynamics (subtle and fast conformational changes prior to and after interaction with cell membranes) and the entirety of the complex biophysical nature of the mechanism of the biological activity of AMPs are essential steps toward the discovery and design of new antimicrobial peptide drugs.

Dr. Juan Borrero
Guest Editor

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Keywords

  • antimicrobial peptides
  • mechanism of biological activity
  • functional diversity of peptides
  • structural analysis of peptides
  • dynamic conformation of peptides
  • lipid composition of the cell membrane
  • peptide–lipid interactions
  • peptide self-association
  • peptide-lipid complex formation
  • peptide–intracellular receptor interaction
  • peptide translocation through membrane
  • cell morphology
  • peptide interaction with infectious agents
  • surface properties of the cell
  • peptide interaction with the cell in vivo

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Published Papers (4 papers)

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Research

20 pages, 2433 KiB  
Article
Production of Pumilarin and a Novel Circular Bacteriocin, Altitudin A, by Bacillus altitudinis ECC22, a Soil-Derived Bacteriocin Producer
by Irene Lafuente, Ester Sevillano, Nuria Peña, Alicia Cuartero, Pablo E. Hernández, Luis M. Cintas, Estefanía Muñoz-Atienza and Juan Borrero
Int. J. Mol. Sci. 2024, 25(4), 2020; https://doi.org/10.3390/ijms25042020 - 7 Feb 2024
Viewed by 1132
Abstract
The rise of antimicrobial resistance poses a significant global health threat, necessitating urgent efforts to identify novel antimicrobial agents. In this study, we undertook a thorough screening of soil-derived bacterial isolates to identify candidates showing antimicrobial activity against Gram-positive bacteria. A highly active [...] Read more.
The rise of antimicrobial resistance poses a significant global health threat, necessitating urgent efforts to identify novel antimicrobial agents. In this study, we undertook a thorough screening of soil-derived bacterial isolates to identify candidates showing antimicrobial activity against Gram-positive bacteria. A highly active antagonistic isolate was initially identified as Bacillus altitudinis ECC22, being further subjected to whole genome sequencing. A bioinformatic analysis of the B. altitudinis ECC22 genome revealed the presence of two gene clusters responsible for synthesizing two circular bacteriocins: pumilarin and a novel circular bacteriocin named altitudin A, alongside a closticin 574-like bacteriocin (CLB) structural gene. The synthesis and antimicrobial activity of the bacteriocins, pumilarin and altitudin A, were evaluated and validated using an in vitro cell-free protein synthesis (IV-CFPS) protocol coupled to a split-intein-mediated ligation procedure, as well as through their in vivo production by recombinant E. coli cells. However, the IV-CFPS of CLB showed no antimicrobial activity against the bacterial indicators tested. The purification of the bacteriocins produced by B. altitudinis ECC22, and their evaluation by MALDI-TOF MS analysis and LC-MS/MS-derived targeted proteomics identification combined with massive peptide analysis, confirmed the production and circular conformation of pumilarin and altitudin A. Both bacteriocins exhibited a spectrum of activity primarily directed against other Bacillus spp. strains. Structural three-dimensional predictions revealed that pumilarin and altitudin A may adopt a circular conformation with five- and four-α-helices, respectively. Full article
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17 pages, 6731 KiB  
Article
New N-Terminal Fatty-Acid-Modified Melittin Analogs with Potent Biological Activity
by Sheng Huang, Guoqi Su, Shan Jiang, Li Chen, Jinxiu Huang and Feiyun Yang
Int. J. Mol. Sci. 2024, 25(2), 867; https://doi.org/10.3390/ijms25020867 - 10 Jan 2024
Cited by 1 | Viewed by 716
Abstract
Melittin, a natural antimicrobial peptide, has broad-spectrum antimicrobial activity. This has resulted in it gaining increasing attention as a potential antibiotic alternative; however, its practical use has been limited by its weak antimicrobial activity, high hemolytic activity, and low proteolytic stability. In this [...] Read more.
Melittin, a natural antimicrobial peptide, has broad-spectrum antimicrobial activity. This has resulted in it gaining increasing attention as a potential antibiotic alternative; however, its practical use has been limited by its weak antimicrobial activity, high hemolytic activity, and low proteolytic stability. In this study, N-terminal fatty acid conjugation was used to develop new melittin-derived lipopeptides (MDLs) to improve the characteristics of melittin. Our results showed that compared with native melittin, the antimicrobial activity of MDLs was increased by 2 to 16 times, and the stability of these MDLs against trypsin and pepsin degradation was increased by 50 to 80%. However, the hemolytic activity of the MDLs decreased when the length of the carbon chain of fatty acids exceeded 10. Among the MDLs, the newly designed analog Mel-C8 showed optimal antimicrobial activity and protease stability. The antimicrobial mechanism studied revealed that the MDLs showed a rapid bactericidal effect by interacting with lipopolysaccharide (LPS) or lipoteichoic acid (LTA) and penetrating the bacterial cell membrane. In conclusion, we designed and synthesized a new class of MDLs with potent antimicrobial activity, high proteolytic stability, and low hemolytic activity through N-terminal fatty acid conjugation. Full article
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10 pages, 1530 KiB  
Article
A Common Polymorphism in RNASE6 Impacts Its Antimicrobial Activity toward Uropathogenic Escherichia coli
by Raul Anguita, Guillem Prats-Ejarque, Mohammed Moussaoui, Brian Becknell and Ester Boix
Int. J. Mol. Sci. 2024, 25(1), 604; https://doi.org/10.3390/ijms25010604 - 3 Jan 2024
Viewed by 839
Abstract
Human Ribonuclease (RNase) 6 is a monocyte and macrophage-derived protein with potent antimicrobial activity toward uropathogenic bacteria. The RNASE6 gene is heterogeneous in humans due to the presence of single nucleotide polymorphisms (SNPs). RNASE6 rs1045922 is the most common non-synonymous SNP, resulting in [...] Read more.
Human Ribonuclease (RNase) 6 is a monocyte and macrophage-derived protein with potent antimicrobial activity toward uropathogenic bacteria. The RNASE6 gene is heterogeneous in humans due to the presence of single nucleotide polymorphisms (SNPs). RNASE6 rs1045922 is the most common non-synonymous SNP, resulting in a G to A substitution that determines an arginine (R) to glutamine (Q) transversion at position 66 in the protein sequence. By structural analysis we observed that R66Q substitution significantly reduces the positive electrostatic charge at the protein surface. Here, we generated both recombinant RNase 6-R66 and -Q66 protein variants and determined their antimicrobial activity toward uropathogenic Escherichia coli (UPEC), the most common cause of UTI. We found that the R66 variant, encoded by the major SNP rs1045922 allele, exhibited superior bactericidal activity in comparison to the Q66 variant. The higher bactericidal activity of R66 variant correlated with an increase in the protein lipopolysaccharide binding and bacterial agglutination abilities, while retaining the same enzymatic efficiency. These findings encourage further work to evaluate RNASE6 SNP distribution and its impact in UTI susceptibility. Full article
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16 pages, 2517 KiB  
Article
Novel Antimicrobial Peptides from Saline Environments Active against E. faecalis and S. aureus: Identification, Characterisation and Potential Usage
by Jakub Lach, Magdalena Krupińska, Aleksandra Mikołajczyk, Dominik Strapagiel, Paweł Stączek and Agnieszka Matera-Witkiewicz
Int. J. Mol. Sci. 2023, 24(14), 11787; https://doi.org/10.3390/ijms241411787 - 22 Jul 2023
Cited by 2 | Viewed by 1158
Abstract
Microorganisms inhabiting saline environments have been known for decades as producers of many valuable bioproducts. These substances include antimicrobial peptides (AMPs), the most recognizable of which are halocins produced by halophilic Archaea. As agents with a different modes of action from that of [...] Read more.
Microorganisms inhabiting saline environments have been known for decades as producers of many valuable bioproducts. These substances include antimicrobial peptides (AMPs), the most recognizable of which are halocins produced by halophilic Archaea. As agents with a different modes of action from that of most conventionally used antibiotics, usually associated with an increase in the permeability of the cell membrane as a result of a formation of channels and pores, AMPs are a currently promising object of research focused on the investigation of antibiotics with non-standard modes of action. The aim of this study was to investigate antimicrobial activity against multidrug-resistant human pathogens of three peptides, which were synthetised based on sequences identified in metagenomes from saline environments. The investigations were performed against Enterococcus faecalis, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli and Candida albicans. Subsequently, the cytotoxicity and haemolytic properties of the tested peptides were verified. An in silico analysis of the interaction of the tested peptides with molecular targets for reference antibiotics was also carried out in order to verify whether or not they can act in a similar way. The P1 peptide manifested the growth inhibition of E. faecalis at a MIC50 of 32 µg/mL and the P3 peptide at a MIC50 of 32 µg/mL was shown to inhibit the growth of both E. faecalis and S. aureus. Furthermore, the P1 and P3 peptides were shown to have no cytotoxic or haemolytic activity against human cells. Full article
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