Fig 1.
Structure of Lassa virus solved using electron cryotomography and sub-tomogram averaging.
(A) A slice through a 3D tomogram of LASV. Three glycoprotein are spikes indicated (white arrowheads). The inset shows a magnified view of the area indicated (dotted line). The membrane (M), matrix (Z), and density bridging a spike to the Z layer (black arrowhead) are indicated. (B) LASV GP spike structure segmented to three spike protomers (different shades of brown), membrane (light blue), and the Z layer (dark blue). Intra-viral tails connecting the spike to the underlying matrix are indicated (arrowhead). (C) One LASV virion is shown cut open highlighting the irregular organization of the glycoprotein spikes, membrane, Z layer, and RNP density (gray).
Table 1.
Data acquisition and processing statistics.
Fig 2.
Structural transitions and LAMP1 binding of the LASV GP spikes upon acidification.
(A) GP structures at different pHs are shown from side (top row) and top (bottom row). All volumes were filtered to 17-Å resolution, rendered at molecular threshold corresponding to the expected molecular mass, and colored as in Fig 1. Residual density corresponding to LAMP1 is colored in green. Inserts in the lower left corners show a close-up of the interface between two spike monomers. Insets in the top right corners show Western blot analysis of GP1 and GP2 subunits. The arrowheads indicate the missing density in the central top part and side of the pH 3 structure.
Fig 3.
Location of the GP1 subunit in the glycoprotein spike.
(A) Crystallographic structure [10](brown ribbon; PDB:4ZJF) was fitted into density (transparent surface) derived by electron cryomicroscopy and subtomogram averaging of GP spikes from virus-like particles at pH 5. The glycans are represented with sticks and colored in green. The histidines indicated in binding of an intracellular receptor (lysosome-associated membrane protein 1, LAMP1) are labeled and colored in red. This triad of histidines faces a crevice (white arrowhead) between the spike subunits. The three-fold symmetry axis is indicated with a black triangle. (B) Same fitting as in A is shown from the side.
Fig 4.
A schematic representation of a hypothetical entry model, derived from the structures determined in this study, is shown. An approximate range of pH in different cellular compartments is depicted as a color gradient from neutral (blue) to very acidic (red). Lassa virus glycoprotein (GP) spike trimer is depicted in three shades of brown and the two different subunits (GP1 and GP2) are labeled. Lysosome-associated membrane protein 1 (LAMP1), an intracellular Lassa virus receptor, is labeled and colored in green. Viral membrane is colored in blue. Different cellular membranes are labeled and colored in gray. Formation of the crevices between GP1 subunits is indicated with white arrows. See text for full description of the entry model.
Fig 5.
Comparison of arenavirus and filovirus glycoprotein spike structures.
Structures of Lassa virus spike (LASV, this study), spike of the arenenavirus-like virus infecting snakes (University of Helsinki Virus, UHL; EMD-2424), and Ebola virus spike (EBOV) with (EMD-6003) and without (EMD-6004) the mucin-like domain are shown at the same scale for comparison.