Figure 2.

Anatomical location of the hotspots to exposed, nonhelical loops and strands of the env protein. The T_h hotspots are highlighted (red) on the crystal structure (34, 37) of gp120 (blue) complexed with CD4 (gray). The structure can be oriented by the position of the N- and C-terminal residues of gp120 and the CD4 binding site. The regions A–C in this figure correspond to A–C in Fig. 1 with the omission of V2 and V3 sequences, absent from the crystal. The composite of all three hotspots is shown from front (D) and side (E) views.