Viral membrane penetration: lytic activity of a nodaviral fusion peptide

The auto-cleavage product from the C-terminal part of the capsid protein of the flock house virus, namely the ₁ peptide, was used as a model peptide to characterize the initial steps of viral membrane penetration. Monolayers at the air–water interface were used to investigate the phase behaviour of ternary lipid–peptide mixtures, whereas solid-supported membranes were used to visualize the lytic activity of the ₁ peptide. 1,2-Dipalmitoyl-sn-glycero-phospatidylcholine/1,2-dipalmitoyl-sn-glycero-phospatidylserine (4:1) membranes were used as negatively charged model membranes. By means of film balance techniques lipid/peptide discrimination was found resulting in a lipid-rich and a peptide-rich phase. Quartz crystal microbalance and scanning force microscopy experiments led to the conclusion of a detergent-like mechanism of the ₁ peptide resulting in mixed lipid–peptide micelles with a molar ratio of 2.8:1. A monolayer adsorption with an ongoing lysis of membranes was found with ₁ peptide molecules interacting at membrane defects.