Fig. 2: Comparison of Tri FPPR Env protomer conformations.

a–c Molecular structures of the three protomers of the Tri FPPR.1 and Tri FPPR.2 Env models were aligned using the gp120 subunits. Conformational differences among the protomers were evident in the gp41 fusion peptide (magenta), the fusion peptide-proximal region (FPPR) and N-terminal heptad repeat (HR1_N) (blue), the α9 helices (orange) and the MPERs (salmon). In contrast, the gp41 HR1_C helices (red) of the three protomers exhibited similar conformations. a The three aligned protomers of the Tri FPPR.1 model are shown in the left panel, and the three aligned protomers of the Tri FPPR.2 model are shown in the right panel. The insets show the gp41 subunits from a different perspective. b. In the left panel, Protomer 2 (darker shading) and Protomer 1 (lighter shading) of the Tri FPPR.1 model are compared. In the right panel, Protomer 3 (darker shading) and Protomer 1 (lighter shading) of the Tri FPPR.1 model are compared. c Protomers 1, 2 and 3 of the Tri FPPR.2 model (darker shading) are compared with the corresponding protomers of the Tri FPPR.1 model (lighter shading).