?Comparative study of the interaction of melittin and lysine peptides with lipid membranes?

MARIA JOSE ELIAS TISSERA; ANIBAL E. DISALVO; ANDREA C. CUTRÓ

Tucuman

Congreso; XLV Reunión Anual Sociedad Argentina de Biofísica 2016; 2017

SAB. Sociedad argentina de Biofísica

Melittin (ML,peptide of bee venom) consisting of 26 amino acids arranged in an α-helix, rich in arginine (Arg) and lysine (Lys). The amphipathic helix penetration into the hydrophobic interior of membranes depends on the membrane composition and ML concentration. This mechanism involves Arg and Lys residues, where their charge distribution can penetrate deep into the acyl chain region and producing defects in membranes. In this context, the objective of this study was to evaluate the interactions of ML and peptides Pentalysine and Tetralysine (same total charge of ML and similar characteristic to the c- terminal ML, respectively) with lipid membranes of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylglyerol (PG) by ζ potential. All the peptides under study have shown to be capable of interacting with the lipid membranes, increasing the surface potential. ML has produced higher changes in ζ potential (at positive values) than the Lys-peptides in DMPC, DMPE and DMPC:DMPG liposomes. The ζ changes observed could be due to a higher affinity of the ML for the bilayer and in the binding sites number. The apparent dissociation constants (Kdapp) have been estimated in order to evaluate the affinity of the peptide interactions with the different lipid membranes. ML interacted with DMPC liposomes with higher affinity than Lys-peptides, this could indicate that beside the electrostatic interaction other forces as hydrophobic ones seems to be involved. On DMPE liposomes, ML and pentalysine show a higher affinity than in DMPC liposomes without significant differences in Kdapp, that could indicate that with this lipid electrostatic forces are the dominants one. The increase of ζ potential produced by ML in this membranes could be due to a higher binding sites for ML or a better exposition of charges in the final disposition in the membrane due its ability to adopt an α-helix. ML in DMPC:DMPG liposomes exhibited the highest changes in the surface potential in comparison with the other tested membranes, but a lower affinity. Finally, the binding of ML and Lys peptides to DMPC and DMPE membranes have showed a Langmuir behavior, in contrast the ML binding to DMPC:DMPG where the interactions seem not be follow a Langmuir one.