Figure 2.

The LASV GP trimer is unique amongst class I glycoproteins. Comparison of the LASV GP trimer to the trimeric structures of the class I glycoproteins from Ebola virus (PDB: 5JQ7), HIV (PDB: 4NCO), Coronavirus (PDB: 5I08), Influenza (PDB: 1RUZ) and Paramyxovirus F (PDB: 2B9B) are shown. For EBOV, HIV, Influenza and CoV, the GP1-equivalent subunit for each virus is colored dark blue and the GP2-equivalent subunit is colored cyan. The three-helix core of each viral glycoprotein and the equivalent region in LASV GP2 is colored yellow. Note: Paramyxoviruses such as PiV5 have two surface glycoproteins, of which F is responsible for fusion of viral and host cell membranes. The larger, carboxy-terminal domain, F1, is colored cyan and the smaller, N-terminal domain, F2, is colored dark blue. A three-helix bundle is formed by the HRB subdomain of F1 and is colored yellow. The C-termini and N-termini of each subunit (GP1 and GP2 equivalent for EBOV, HIV, Influenza and CoV and F1 and F2 for PiV 5) are shown as spheres and indicated by arrows. (b) Comparison between prefusion LASV GP2 and postfusion GP2 of LCMV (PDB: 3MKO), a close relative of LASV. In the prefusion conformation of LASV GP2, HR1 (yellow) is broken up into four segments (HR1a-d) and connected to HR2 through the T-loop (pink), which forms a β-sheet with β1 of GP1. In contrast, in the postfusion conformation of GP2, HR1 forms a single α helix while the T-loop forms an α helix. The relative locations of the viral membrane in the prefusion state and the fused viral and host cell membranes in the postfusion state are indicated. The fusion peptide residues were not included in the postfusion GP2 crystallization construct but would be embedded in the fused membranes.