Hydrophobic Substitutions In The First Residue Of The Crac Segment Of The Gp41 Protein Of Hiv

We investigated the peptides N-acetyl-AWYIK-amide and N-acetyl-VWYIK-amide
corresponding to single amino acid substitutions in LWYIK, a segment found in the
gp41 protein of HIV and believed to play a role in sequestering this protein to a
cholesterol-rich domain in the membrane. The effects of these peptides on the
thermotropic phase transitions of 1-stearoyl-2-oleoylphosphatidylcholine (SOPC)
and mixtures of SOPC and cholesterol were intermediate between that having the
wild-type sequence (LWYIK) and another (IWYIK), the least active peptide
previously studied. This correlated with results from studies of single mutations
in the gp41 protein of HIV-1, in which L679 of the LWYIK segment is replaced with
either A or V, measuring the capability of TZM-BL HeLa-based HIV-1 indicator
cells to form syncytia. The peptides were also comparatively analyzed in silico.
All together, the results suggest that the mode of interaction of this region of
gp41 with the polar heads of membrane lipids contributes to its cholesterol
selectivity and that this is somehow related to the biological activity of the
viral glycoprotein.