FIG 5.

Orientation of the bridging sheet hairpins in relation to the V3 loop. The hairpins that constitute the bridging sheet (hairpins 1 and 2, shown in blue and red, respectively) and the V3 loop (green) are shown in the CD4-liganded conformation (PDB accession number 2B4C). Note that hairpin 1 (β2-β3) is the base for the V1/V2 loops (the V1/V2 loops are missing in the crystal structure) and that the V3 loop protrudes between the proximal and distal aspects of hairpin 2 (β20-β21). The locations of the different V3 loop truncations (V3 base and ΔV3) are marked with dashed lines. For the sake of consistency with our mutants, the numbering is based on BaL gp120 (see Materials and Methods).