Abstract
Plantaricin149a (Pln149a) is a cationic antimicrobial peptide, which was suggested to cause membrane destabilization via the carpet mechanism. The mode of action proposed to this antimicrobial peptide describes the induction of an amphipathic α-helix from Ala7 to Lys20, while the N-terminus residues remain in a coil conformation after binding. To better investigate this assumption, the purpose of this study was to determine the contributions of the Tyr1 in Pln149a in the binding to model membranes to promote its destabilization. The Tyr to Ser substitution increased the dissociation constant (KD) of the antimicrobial peptide from the liposomes (approximately three-fold higher), and decreased the enthalpy of binding to anionic vesicles from −17.2 kcal/mol to −10.2 kcal/mol. The peptide adsorption/incorporation into the negatively charged lipid vesicles was less effective with the Tyr1 substitution and peptide Pln149a perturbed the liposome integrity more than the analog, Pln149S. Taken together, the peptide-lipid interactions that govern the Pln149a antimicrobial activity are found not only in the amphipathic helix, but also in the N-terminus residues, which take part in enthalpic contributions due to the allocation at a lipid-aqueous interface.
Highlights
IntroductionSeveral antimicrobial peptides (AMPs) are able to simultaneously attack various microorganisms (including bacteria, fungi, and enveloped viruses [1,2]) and exhibit cytotoxic activity towards tumor cells [3]
Several antimicrobial peptides (AMPs) are able to simultaneously attack various microorganisms and exhibit cytotoxic activity towards tumor cells [3]
AMPs have been identified from different sources, the bacteriocins [15] are one of the most investigated groups, mainly the members isolated from lactic acid bacteria (LAB) [16,17,18], which were shown to vary widely in size, primary and secondary structures [19,20], but at the same time share some common features: cationicity, amphiphilicity, and act by altering the permeability of cellular membranes [21,22]
Summary
Several antimicrobial peptides (AMPs) are able to simultaneously attack various microorganisms (including bacteria, fungi, and enveloped viruses [1,2]) and exhibit cytotoxic activity towards tumor cells [3]. C11, which displays antimicrobial activity against certain sensitive strains by membrane permeabilization, its primary function is considered to act as a peptide pheromone, controlling the production of antimicrobial peptides in Lactobacillus plantarum C11. Both are differential activities with different bacterial strains. In a similar way to PlnA, the peptide Plantaricin149 (Pln149), produced by L. plantarum NRIC 149, is cationic in nature, composed of 22 amino acid residues with inhibitory activity against some pathogenic bacteria [27,28] with high minimum inhibitory concentration (MIC) values [27,29], compared to the MIC of other LAB bacteriocins [26]. The molecular model of the whole Pln149a sequence, created by SP3 software, is a helix structure which was proposed to extend from the residue
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