The ebolavirus glycoprotein (GP) is the only virally expressed protein on the virion surface and is critical for attachment to and fusion with host cells. Hence, EBOV GP is the critical target of neutralizing antibodies and is an important component of vaccines. The Zaire ebolavirus (ZEBOV) surface glycoprotein contains 676 amino acids and is post-translationally cleaved by furin into two disulfide-linked subunits: GP1 and GP2. Three GP1-GP2 units form a 450 kDa trimeric spike on the virus surface. GP1 contains an N-terminal signal sequence, a putative receptor-binding site and a heavily glycosylated mucin-like domain. GP2 contains an internal fusion loop, two heptad-repeat regions separated by a CX 6CC disulfide motif, an ∼30-residue transmembrane anchor and a four-residue C-terminal cytoplasmic tail.