Structural characterization of the transmembrane proximal region of the hepatitis C virus E1 glycoprotein

A detailed knowledge of the mechanism of virus entry represents one of the most promising approaches to develop new therapeutic strategies. However, viral fusion is a very complex process involving fusion glycoproteins present on the viral envelope. In the two Hepatitis C virus envelope proteins, E1 and E2, several membranotropic regions with a potential role in the fusion process have been identified. Among these, we have selected the 314-342 E1 region. Circular Dichroism data indicate that the peptide exhibits a clear propensity to adopt a helical folding in membrane mimicking media, from mixture as (HFIP/H2O or TFE/H2O) to phospholipisds with a slight preference to negative charged bilayers. The 3D structure of E1314-342 peptide, calculated by 2D- NMR in a low-polarity environment, presents two helical stretches encompassing residues 319-323 and 329-338 respectively. The peptide, presenting a largely apolar character, interacts with liposomes, as indicated by fluorescence and ESR spectra. The strength of the interaction and the deepness of peptide insertion in the phospholipid membrane is modulated by the bilayer composition, the interaction with anionic phospholipids being among the strongest ever observed. The presence of cholesterol also enhances the peptide-bilayer interaction, favoring the peptide positioning close to the bilayer surface. Overall, the experimental data support the idea that this region of E1 might be involved in membrane destabilization and viral fusion, therefore it may represent a good target to develop anti-viral molecules.