The structure and membrane interaction of the internal fusion
peptide (IFP) fragment of the
avian sarcoma and leucosis virus (ASLV) envelope
glycoprotein was studied by an array of biophysical methods. The
peptide was found to induce
lipid mixing of vesicles more strongly than the fusion
peptide derived from the N-terminal fusion
peptide of influenza virus (HA2-FP). It was observed that the helical structure was enhanced in association with the model membranes, particularly in the N-terminal portion of the
peptide. According to the infrared study, the
peptide inserted into the membrane in an oblique orientation, but less deeply than the
influenza HA2-FP. Analysis of NMR data in
sodium dodecyl sulfate micelle suspension revealed that Pro13 of the
peptide was located near the
micelle-water interface. A type II beta-turn was deduced from NMR data for the
peptide in aqueous medium, demonstrating a conformational flexibility of the IFP in analogy to the N-terminal FP such as that of gp41. A loose and multimodal self-assembly was deduced from the
rhodamine fluorescence self-quenching experiments for the
peptide bound to the membrane bilayer. Oligomerization of the
peptide and its variants can also be observed in the electrophoretic experiments, suggesting a property in common with other N-terminal FP of class I fusion
proteins.