Interaction Between Lytic Peptide Latarcin 2A and Supported Lipid Bilayers Studied by in Situ Atomic Force Microscopy

Abstract

Latarcin 2a (ltc2a, GLFGKLIKKFGRKAISYAVKKARGKH-COOH) is one of the seven short linear antimicrobial and cytolytic peptides extracted from the venom of the Central Asian spider, Lachesana tarabaevi, with lytic activity against Gram-positive and Gram-negative bacteria, erythrocytes, and yeast at micromolar concentrations. Ltc2a is known to adopt helix-hinge-helix conformation in membrane mimicking environment, whereas its derivative latarcin 2aG11A (ltc2aG11A, GLFGKLIKKFARKAISYAVKKARGKH-COOH), likely adopts a more rigid helical structure, has higher nonspecific interaction with zwitterionic membrane and is potentially more toxic against eukaryotic cells. In this work, interactions of two ltc2a derivatives with supported lipid bilayers (DOPC/egg SPM/Chol 40/40/20 mol%) were studied by in situ atomic force microscopy. Interactions are affected by membrane fluidity and peptide concentration. Both peptides induced reorganization of raft model membrane by reducing line tension of the liquid ordered phase. Ltc2aG11A-induced raft membrane thinning may be due to membrane interdigitation. Presence of cholesterol was determined to be important to attenuate peptide induced membrane disruption. Finally, leakage assay showed both peptides have similar membrane permeability toward various model membrane vesicles.