Structure models of FE Env, gp120 and gp41. a) Two views of the model of the FE gp120 monomer with grafted V1/V2 domain (see Methods). The gp120 monomer consists of four domains: the inner domain (light blue), the outer domain (light pink), the bridging sheet (orange), and the V1/V2 loop (dark blue). The 4 beta stranded bridging sheet forms upon CD4 binding near the CD4 binding loop (yellow). The V3 loop (light green) extends from the outer domain. Mutated PNGS that increase or decrease viral neutralization by any of the MAbs are shown as red sticks, and sites with negligible effects are shown as blue sticks. b) Two views of the model of the FE gp41 six helix bundle (see Methods). The three alpha helices in the middle are shown in cyan, and the three helices on the outside are in green. Mutated PNGS N625 and N637 are shown as red sticks. Aromatic residues W678, W680, and Y681 (yellow) from the MPRE region extend from the tip of each monomer and are proposed to insert into the viral membrane (only one set of residues shown).