1.G.9.2.3
The Human T-cell leukemia virus 1, HTLV-1, of 488 aas and 2 TMSs, N- and C-terminal. The glycine-rich region of this transmembrane protein is involved in membrane fusion. It is a class I viral fusion protein (Wilson et al. 2005). The N-terminal fusion peptide initiates virus-cell membrane fusion. The fusion peptide is linked to the coiled-coil core through a conserved sequence that is rich in glycines. Wilson et al. 2005 investigated the functional role of the glycine-rich segment, Met-326 to Ser-337, of gp21. Alanine substitution for the hydrophobic residue Ile-334 caused a 90% reduction in cell-cell fusion activity without a detectable effect on the lipid-mixing and pore forming phases of fusion. Retroviral glycoprotein fusion thus appears to require flexibility within the glycine-rich segment and hydrophobic contacts mediated by this segment (Wilson et al. 2005).