Abstract :
[en] Previous results indicate that the external glycoprotein gp51 of bovine leukemia
virus plays an important role in the process of cell fusion induced by bovine
leukemia virus (Bruck, C., Mathot, S., Portetelle, D., Berte, C., Franssen, J.
D., Herion, P., and Burny, A. (1982) Virology 122, 342-352; Voneche, V.,
Portetelle., D., Kettmann, R., Willems, L., Limbach, K., Paoletti, E.,
Ruysschaert, J. M., Burny, A., and Brasseur, R. (1992) Proc. Natl. Acad. Sci. U.
S. A. 89, 3810-3814) and suggest that a region encompassing residues 23 and 25 of
gp51 is involved in this process (Portetelle, D., Couez, D., Bruck, C., Kettmann,
R., Mammerickx, M., Van der Maaten, M., Brasseur, R., and Burny, A. (1989)
Virology 169, 27-33; Mamoun, R., Morisson, M., Rebeyrotte, N., Busetta, B.,
Couez, D., Kettmann, R., Hospital, M., and Guillemain, B. (1990) J. Virol. 64,
4180-4188). X-ray diffraction studies performed on envelope glycoproteins of
influenza virus indicate that the NH2-terminal part of the external glycoprotein
lies very close to the fusion peptide. The same overall structure seems to exist
in human immunodeficiency virus as suggested by site-directed mutagenesis
followed by syncytia induction assays. Our theoretical studies indicate that a
segment expanding between residues 19 and 27 of gp51 probably adopts an
amphipathic beta-strand structure. We hypothesize that the amphipathic 19-27
structure of gp51 plays an important role in the process of membrane fusion by
interacting with the fusion peptide or with another region of gp30. Mutational
analysis disrupting the amphipathy of the 19-27 region strongly altered the
fusogenic capacity of the gp51-gp30 complex.
