Lipid membrane fusion induced by the human immunodeficiency virus type 1 gp41 N-terminal extremity is determined by its orientation in the lipid bilayer.
The amino-terminal extremity of the human immunodeficiency virus type 1 transmembrane protein (gp41) is thought to play a pivotal role in the fusion of virus membranes with the plasma membrane of the target cell and in syncytium formation. Peptides with sequences taken from the human immunodeficiency virus type 1 gp41 fusogenic (synthetic peptides SPwt and SP-2) and nonfusogenic (SP-3 and SP-4) glycoproteins adopt mainly a beta-sheet conformation in the absence of lipid, as determined by attenuated total reflection Fourier transform infrared spectroscopy, and after interaction with large unilamellar liposomes, the beta-sheet is partly converted into an alpha-helical conformation. Peptides SPwt and SP-2 but not SP-3 or SP-4 were able to promote lipid mixing as assessed by fluorescence energy transfer assay and dye leakage in a vesicle leakage assay. By using polarized attenuated total reflection Fourier transform infrared spectroscopy, SPwt and SP-2 were found to adopt an oblique orientation in the lipid membrane whereas SP-3 and SP-4 were oriented nearly parallel to the plane of the membrane. These findings confirm the correlation between the membrane orientation of the alpha-helix and the lipid mixing ability in vitro. Interestingly, the data provide a direct correlation with the fusogenic activity of the parent glycoproteins in vivo.
Martin
I
I
Laboratoire de Chimie-Physique des Macromolécules aux Interfaces, Université Libre de Bruxelles, Belgium.
Schaal
H
H
Scheid
A
A
Ruysschaert
J M
JM
D000595:Amino Acid Sequence; D001665:Binding Sites; D004396:Coloring Agents; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008051:Lipid Bilayers; D008561:Membrane Fusion; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017550:Spectroscopy, Fourier Transform Infrared
D004396:Coloring Agents; D015700:HIV Envelope Protein gp41; D008051:Lipid Bilayers