Fig. 1.
Expression constructs. (Upper) Schematic representations of HIV-1 envelope glycoproteins; gp160, the full-length precursor. Various segments of gp120 and gp41 are designated as follows: C1–C5, conserved regions 1–5; V1–V5, variable regions 1–5; F, fusion peptide; HR1, heptad repeat 1; C–C loop, immunodominant loop with a conserved disulfide bond; HR2, heptad repeat 2; (see SI Fig. 9 for alignment); TM, transmembrane anchor; CT, cytoplasmic tail. Expression constructs are: gp140, uncleaved ectodomain of gp160 with a C-terminal His tag; gp140-Fd, uncleaved ectodomain of gp160 with a trimerization tag and a C-terminal His tag; gp41-inter, gp41 in the prehairpin intermediate conformation trapped by an N-terminal HR2 peptide and a C-terminal foldon tag; gp41-post, gp41 in the six-helix conformation with partial MPER. Glycans are represented by tree-like symbols. (Lower) Diagrams represent 3D organization of these protein species. Gp120 and gp41 in the prefusion state are shown in light green and light blue, respectively. The viral membrane is in orange. Other regions are colored as in the schematics above.