Figure 2.

The structure of E2 Env. (a) The structure of H77 E2c (PDB: 4MWF) with the molecular surface color-coded as in Figure 1. The structures of E2 core domain reveal a novel protein fold consisting of a central immunoglobulin (Ig) β-sandwich fold (red), which is stabilized by the conserved disulfide bonds and flanked by an N-terminal front layer (cyan) and a C-terminal back layer (green). The long CD81 binding loop (blue) extends from the central β-sandwich domain. (b) E2 neutralization antigenic sites mapped onto the H77 E2c surface. The AR1 immune decoy site is also shown. AR3 is marked in dashed line, and AS412, AS434, and AR1 are colored in pink, yellow, and green, respectively. The mAbs that were used for structural studies and epitope characterization are listed.