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Differential interactions of the antimicrobial peptide, RQ18, with phospholipids and cholesterol modulate its
Claudiane V Almeida1, Caio F R de Oliveira2, Edson L Dos Santos3
1Universidade Federal de Mato Grosso do Sul, Campo Grande, Mato Grosso do Sul, Brazil.
Background:
Antimicrobial peptides (AMPs) are molecules with potential application for the treatment of microorganism infections. We, herein, describe the structure, activity, and mechanism of action of RQ18, an α-helical AMP that displays antimicrobial activity against Gram-positive and Gram-negative bacteria, and yeasts from the Candida genus.
Methods:
A physicochemical-guided design assisted by computer tools was used to obtain our lead peptide candidate, named RQ18. This peptide was assayed against Gram-positive and Gram-negative bacteria, yeasts, and mammalian cells to determine its selectivity index. The secondary structure and the mechanism of action of RQ18 were investigated using circular dichroism, large unilamellar vesicles, and molecular dynamic simulations.
Results:
RQ18 was not cytotoxic to human lung fibroblasts, peripheral blood mononuclear cells, red blood cells, or Vero cells at MIC values, exhibiting a high selectivity index. Circular dichroism analysis and molecular dynamic simulations revealed that RQ18 presents varying structural profiles in aqueous solution, TFE/water mixtures, SDS micelles, and lipid bilayers. The peptide was virtually unable to release carboxyfluorescein from large unilamellar vesicles composed of POPC/cholesterol, model that mimics the eukaryotic membrane, indicating that vesicles' net charges and the presence of cholesterol may be related with RQ18 selectivity for bacterial and fungal cell surfaces.
Conclusions:
RQ18 was characterized as a membrane-active peptide with dual antibacterial and antifungal activities, without compromising mammalian cells viability, thus reinforcing its therapeutic application.
General Significance:
These results provide further insight into the complex process of AMPs interaction with biological membranes, in special with systems that mimic prokaryotic and eukaryotic cell surfaces.
Insights
RQ18, a novel antimicrobial peptide (AMP), effectively targets bacteria and fungi without harming human cells. Its membrane-active nature and high selectivity index show therapeutic potential for infections.
Area of Science:
- Biochemistry
- Molecular Biology
- Drug Discovery
Background:
- Antimicrobial peptides (AMPs) are crucial for combating microorganism infections.
- RQ18 is an alpha-helical AMP with demonstrated activity against Gram-positive and Gram-negative bacteria and Candida yeasts.
Purpose of the Study:
- To characterize the structure, activity, and mechanism of action of the novel peptide RQ18.
- To evaluate the therapeutic potential and selectivity of RQ18 against various microorganisms and mammalian cells.
Main Methods:
- Computer-aided physicochemical design was employed to develop RQ18.
- Antimicrobial activity, selectivity index, secondary structure, and membrane interaction mechanisms were assessed using assays with bacteria, yeasts, mammalian cells, circular dichroism, and molecular dynamics simulations.
Main Results:
- RQ18 exhibited potent antibacterial and antifungal activity with a high selectivity index, showing no cytotoxicity to human lung fibroblasts, PBMCs, red blood cells, or Vero cells.
- Structural analysis revealed RQ18's adaptability in different environments, with its interaction with lipid bilayers influenced by charge and cholesterol content, suggesting selective targeting of microbial membranes.
Conclusions:
- RQ18 is a membrane-active peptide with dual antibacterial and antifungal properties.
- Its non-cytotoxic nature towards mammalian cells supports its potential as a therapeutic agent for microbial infections.
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