Interaction between the NS4B amphipathic helix, AH2, and charged lipid headgroups alters membrane morphology and AH2 oligomeric state — Implications for the Hepatitis C virus life cycle

AbstractThe non-structural protein 4B (NS4B) from Hepatitis C virus (HCV) plays a pivotal role in the remodelling of the host cell's membranes, required for the formation of the viral replication complex where genome synthesis occurs. NS4B is an integral membrane protein that possesses a number of domains vital for viral replication. Structural and biophysical studies have revealed that one of these, the second amphipathic N-terminal helix (AH2), plays a key role in these remodelling events. However, there is still limited understanding of the mechanism through which AH2 promotes these changes. Here we report on solid-state NMR and molecular dynamics studies that demonstrate that AH2 promotes the clustering of negatively charged lipids within the bilayer, a process that reduces the strain within the bilayer facilitating the remodelling of the lipid bilayer. Furthermore, the presence of negatively charged lipids within the bilayer appears to promote the disassociation of AH2 oligomers, highlighting a potential role for lipid recruitment in regulating NS protein interactions

Molecular dynamic studies of the antimicrobial peptide Dermaseptin B2 and its derivative Dermaseptin DS01

Rapid development of resistance to antimicrobials and the lack of new therapy development are critical issues facing infectious disease treatment globally. Over the past two decades, antimicrobial peptides (AMPs) have been extensively researched and shown to exhibit broad-spectrum activity against various microbes, viruses, fungi and even cancerous cells, thus they are thought to have the solution to the increasing resistance problem. Understanding the role that antimicrobial peptides play in preventing infections is essential if these peptides are to form a new class of clinically effective antimicrobial agents and for them to be used therapeutically in humans. This research will look at a family of antimicrobial peptides known as Dermaseptin that are secreted by an Amazonian frog species. These peptides have shown potent activity against Gram-negative and positive bacteria, viruses, fungi and cancer cells. They exhibit bacterial colony inhibition effect at the micromolar concentration level with minimal effect on host cells. For its high potency and lack of toxicity to host cell, the Dermaseptin family appears to have therapeutic potential and this thesis will attempt to understand how they interact with membranes at the molecular level using coarse-grained computational models and simulations