Figure 1: Temperature-dependent changes in DENV1 and 2 accompanying transmission from mosquito vector (28 °C) to human host (37 °C).

Cryo-EM structures of DENV1 and DENV2 icosahedral particles (Triangulation, T=3) showing symmetry units of E-proteins straddling the five-fold (pentamer), two-fold (dimer) and three-fold (trimer) vertices in dark, medium and light blue respectively. The triangle highlights a single symmetry unit and the numbers indicate the five-fold, three-fold vertices and two-fold midpoint. Left, cryo-EM structure of smooth, compact DENV2 (PDB ID: 3J27, 3.5 Å resolution) and DENV1 (PDB ID: 4CCT, 4.5 Å resolution) at 28 °C (environment inside the mosquito vector). Right, cryo-EM structure of expanded DENV2 (PDB ID: 3ZKO, 13 Å resolution) and unexpanded DENV1 (PDB ID: 4CCT, 4.5 Å resolution) at 37 °C (environment within human host following transmission). White spaces at three-fold icosahedral vertices indicate exposed regions of the lipid bilayer upon expansion. Inset 1: DENV structural proteome. Cryo-EM structures of DENV E (blue) (PDB ID: 3J27) and M (yellow) (PDB ID: 3J27) proteins shown in the context of the viral structure. The lipid bilayer is highlighted in dark grey. Since C-proteins are not observable in the cryo-EM structures of intact DENVs, an approximate position (region coloured red) based on its proposed role in bridging the RNA genome (not shown) beneath the lipid bilayer is represented. Inset 2: NMR structure of C (red) (PDB ID: 1R6R) protein dimer. The N and C-termini of one C-monomer are labelled.