The major envelope protein, GP64, of 512 aas and 2 TMSs (N- and C-terminal).  The two fusion peptides of this type III bipartite system are residues 75 - 88 and 145 - 160 (Apellániz et al. 2014). The GP64 transmembrane domain is essential for GP64 trafficking, membrane fusion, virion budding, and virus infectivity but could be replaced only by transmembrane domains from related viral membrane proteins (Li and Blissard 2008).