Figure 1. Transcription and processing of Zaire ebolavirus glycoproteins.

The primary open reading frame of ebolavirus GP encodes a sGP (shown as white and red rectangles). Proteolytic cleavage of pre-sGP by furin results in the formation of the mature sGP and a small nonstructural fragment, termed Δ-peptide. Co-transcriptional stuttering of the GP gene results in two additional glycoproteins: GP and ssGP. GP is the virion-attached glycoprotein and proteolytic cleavage of its precursor (pre-GP) by furin results in two subunits, GP₁ and GP₂, that remain linked by a disulfide bond. The GP₁ and GP₂ heterodimer trimerizes and forms the viral surface peplomer. TNF-α-converting enzyme can also cleave envelope GP, at a site proximal to the GP₂ transmembrane domain, thereby releasing a soluble trimeric GP. ssGP is a small secreted glycoprotein that shares the first 295 amino acids with sGP and GP, but has a different C-terminus (two nonshared residues, as colored in yellow). It has been reported that ssGP forms a monomer in solution. GP: Glycoprotein; sGP: Secreted glycoprotein; ssGP: Small, secreted glycoprotein; TACE: TNF-α-converting enzyme; TM: Transmembrane anchor.