Viral Fusion Peptide Interactions with Lipid Bilayers Studied by Neutron Scattering*

The HIV-1 virus infects a target cell through a process that begins with binding to the surface of the cell membrane and then fusing with it. Key to the process is a short sequence at the end of the gp41 capsid protein, which is called the fusion peptide (FP). The isolated FP can also cause vesicles to fuse, a process that involves a conformational transition that depends on peptide concentration and the composition of the membrane.  Here, the dependence of the lipid composition, specifically the acyl chain composition, on the behavior of the FP was studied by neutron spin echo spectroscopy, small-angle neutron scattering and circular dichroism spectroscopy.  The results indicate that the behavior of the FP depends strongly on the unsaturated acyl chain composition of the membrane but suggest that the behavior does not depend on the composition in a linear fashion. The present results provide new insight into how the FP conformational transition drives vesicle fusion.