Structural Features of Peptides Derived from Feline Immunodeficiency Virus Tm-glycoprotein

Feline immunodeficiency virus (FIV) is a pathogen that causes an AIDS-like syndrome in domestic cats and is extensively used as a model system by which criteria for anti-lentiviral vaccines and drugs development can be tested. Despite little homology sequence, the surface and TM gp of FIV and HIV-1 exhibit a common structural framework and appear to play similar roles in Initiation of cell infection mediating the final event of membrane fusion and virus entry. Recently a 20-mer synthetic peptide spanning amino acids 767L-G786 of the membrane-proximal ectodomain of FIV (TM) gp gp41(767-786)was found to be endowed with potent antiviral activity. Testing deleted or substituted peptides, the 8-mer gp41(770-777), designated C8, including in the sequence three Trp residues was identified as the minimal sequence needed for full antiviral activity. NMR conformational analysis of gp41(770-777) evidenced the presence of a b-turn conformation centered on the residues 773-776. Here we report the conformational analysis of the 20-mer TM-767-786 by means of NMR spectroscopy. A comparison between structural properties of gp41(767-786) and of gp41(770-777) was carried out in order to define the role played by the sequence length and by the Trp side chains on the active fragments stability.