Fig. 3: Negative-stain EM analysis of HCV-1 sE1E2.Cut1+2.SPYΔN-His6 bound to NAbs.
a Selected 2D class averages (top) and EM density maps from 3D reconstructions (bottom) of sE1E2 in complex with AR3C (left), AR4A (middle), or both AR3C and AR4A (right). Atomic models were fitted into the corresponding density maps to aid structural interpretation. b Selected 2D class averages (top) and 3D EM density maps (bottom) of sE1E2 bound to NAb combinations: AR1B and AR3C (left), AR5A and AR4A (middle), and AR2A, AR1B, and AR3C (right). In (a, b), maps and fitted models are shown in two orientations (rotated 180°) to provide alternative views of the sE1E2/NAb interfaces. c Epitope mapping of antigenic regions AR1–5 on the surface of HCV-1 sE1E2.Cut1+2.SPYΔN-His6. AR1, AR2, and AR5 epitope locations were inferred from negative-stain EM reconstructions of complexes with AR1B, AR2A, and AR5A, respectively. In (a–c), models were fitted into EM densities using the cryo-EM structure of engineered sE1E2.SZ bound to HEPC74 and AR4A (PDB ID: 8FSJ), the crystal structure of the E2mc3/AR3C complex (PDB ID: 6UYD), and the crystal structure of SpyTag/SpyCatcher (PDB ID: 4MLI).
