Membrane Binding and Antimicrobial Activity of a Catioinc, Porphyrin-Binding Peptide

Abstract

that the antimicrobial activity of these peptides can be correlated to the 3D-hydrophobic moment and to a simple structure-based packing parameter. This suggests that, in principle, one could design antimicrobial peptides based on such parameters. Our study shows that the nature of histidine favors its interaction with anionic lipid headgroups, i.e., a location at one end of an AMP, instead of the middle, and enhances the aggregation of cationic AMPs around anionic lipids, leading to transmembrane pore formation. The latter mechanism of disruption of the membrane can be correlated with the increased antimicrobial activity of these AMPs. Hence, the position of the histidine within the peptide sequence can be linked with AMP's mechanism of interaction with the membrane surface. Furthermore, the presence of histidine residue reduced the cytotoxic and hemolytic activity of the peptides, in some cases maintaining the same efficacy against bacteria. Some of these peptides have the potential to become good candidates to fight against bacteria. Acknowledgments: This work was supported by a grant of the Romanian National Authority for Scientific Research, CNDI-UEFISCDI, project number PNII-123/2012, PNII-98/2012, PN-II-ID-PCCE-2011-2-0027, PN 09370301 and PN-II-RU-TE-2014-4-2418. Antimicrobial peptides (AMPs) are cationic, amphipathic proteins with an innate ability to kill a wide variety of pathogens, including viruses, fungi and bacteria. AMPs can be grouped into two general categories based on their mechanism of action. One group acts via permeabilization, or disruption of the cell membrane. The other group acts via translocation, or diffusion across the cell membrane and disruption of an intracellular process. Confocal microscopy is a technique readily used to identify AMP methods of action as it allows researchers to visualize peptide localization in bacteria by taking cross sections of cells. However, the small size and different orientations of bacteria can produce low-resolution images. To combat this problem our lab has used the cell-wall deficient spheroplast form of Escherichia coli to obtain higher quality images. Thesespheroplasts are both spherical and larger than typical E. coli, leading to improved imaging. Previously, we showed that several previously characterized AMPs have the same behavior against E. coli spheroplasts as normal cells. This project is an extension of that work aimed at developing protocols to consider the visualization of AMPs with cell-wall deficient forms of other bacterial strains. Characterizing AMPs against a variety of bacteria is important as research shows that AMPs antimicrobial properties differ against different bacteria strains. To this end, we are developing protocols to form protoplasts of the gram-positive bacteria Bacillus subtilis and Bacillus megaterium for imaging with well-characterized control peptides, such as buforin II and magainin. We have also investigated the membrane integrity of cell-wall deficient bacteria using a microscopy-based permeabilization assay. 1...

Fabrication of Bis-Quaternary Ammonium Salt as an Efficient Bactericidal Weapon Against Escherichia coli and Staphylococcus aureus

“…More than 1.3 million deaths of children are reported to be caused by diarrheal illness worldwide every year, indicating the urgent necessity to develop new antibacterial agents with favorable safety and potent antibacterial activity. To this end, a variety of antibacterial materials, such as antibiotics, antimicrobial peptides, cationic polymers, carbon-based nanomaterials, − small molecular antibacterial agents, − and metals or metal oxides − have been widely used in antimicrobial research. Among these traditional methods, the use of antibiotics is the most common and effective approach to treat bacterial infectious diseases .…”