Multiple Antimicrobial Effects of Hybrid Peptides Synthesized Based on the Sequence of Ribosomal S1 Protein from Staphylococcus aureus

The need to develop new antimicrobial peptides is due to the high resistance of pathogenic bacteria to traditional antibiotics now and in the future. The creation of synthetic peptide constructs is a common and successful approach to the development of new antimicrobial peptides. In this work, we use a simple, flexible, and scalable technique to create hybrid antimicrobial peptides containing amyloidogenic regions of the ribosomal S1 protein from Staphylococcus aureus. While the cell-penetrating peptide allows the peptide to enter the bacterial cell, the amyloidogenic site provides an antimicrobial effect by coaggregating with functional bacterial proteins. We have demonstrated the antimicrobial effects of the R23F, R23DI, and R23EI hybrid peptides against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa, Escherichia coli, and Bacillus cereus. R23F, R23DI, and R23EI can be used as antimicrobial peptides against Gram-positive and Gram-negative bacteria resistant to traditional antibiotics.

The Effect of Conjugation with Octaarginine, a Cell-Penetrating Peptide on Antifungal Activity of Imidazoacridinone Derivative

Acridine cell-penetrating peptide conjugates are an extremely important family of compounds in antitumor chemotherapy. These conjugates are not so widely analysed in antimicrobial therapy, although bioactive peptides could be used as nanocarriers to smuggle antimicrobial compounds. An octaarginine conjugate of an imidazoacridinone derivative (Compound 1-R8) synthetized by us exhibited high antifungal activity against reference and fluconazole-resistant clinical strains (MICs ≤ 4 μg mL−1). Our results clearly demonstrate the qualitative difference in accumulation of the mother compound and Compound 1-R8 conjugate into fungal cells. Only the latter was transported and accumulated effectively. Microscopic and flow cytometry analysis provide some evidence that the killing activity of Compound 1-R8 may be associated with a change in the permeability of the fungal cell membrane. The conjugate exhibited low cytotoxicity against human embryonic kidney (HEK-293) and human liver (HEPG2) cancer cell lines. Nevertheless, the selectivity index value of the conjugate for human pathogenic strains remained favourable and no hemolytic activity was observed. The inhibitory effect of the analysed compound on yeast topoisomerase II activity suggested its molecular target. In summary, conjugation with R8 effectively increased imidazoacridinone derivative ability to enter the fungal cell and achieve a concentration inside the cell that resulted in a high antifungal effect.

Imaging of the Entry Pathway of a Cell-Penetrating Peptide–DNA Complex From the Extracellular Space to Chloroplast Nucleoids Across Multiple Membranes in Arabidopsis Leaves

Each plant cell has hundreds of copies of the chloroplast genome and chloroplast transgenes do not undergo silencing. Therefore, chloroplast transformation has many powerful potential agricultural and industrial applications. We previously succeeded in integrating exogenous genes into the chloroplast genome using peptide–DNA complexes composed of plasmid DNA and a fusion peptide consisting of a cell-penetrating peptide (CPP) and a chloroplast transit peptide (cpPD complex). However, how cpPD complexes are transported into the chloroplast from outside the cell remains unclear. Here, to characterize the route by which these cpPD complexes move into chloroplasts, we tracked their movement from the extracellular space to the chloroplast stroma using a fluorescent label and confocal laser scanning microscopy (CLSM). Upon infiltration of cpPD complexes into the extracellular space of Arabidopsis thaliana leaves, the complexes reached the chloroplast surface within 6h. The cpPD complexes reached were engulfed by the chloroplast outer envelope membrane and gradually integrated into the chloroplast. We detected several cpPD complexes localized around chloroplast nucleoids and observed the release of DNA from the cpPD. Our results thus define the route taken by the cpPD complexes for gene delivery from the extracellular space to the chloroplast stroma.