Fig 4.

Solution small-angle X-ray scattering structures for full-length gp120 monomer in complex with D1D2 sCD4. (A) SAXS pattern for the full-length, glycosylated gp120-sCD4 complex. Solid black line represents the calculated SAXS pattern for a typical DAMMIN reconstruction. Inset shows the Guinier fit. (B) Corresponding P(r) pairwise distance distribution plot. (C) “Averaged” SAXS structures for the gp120-sCD4 complex, shown as an envelope drawn over the averaged, filtered DAMMIN structure (see Fig. S3 in the supplemental materia). Structures for gp120 core with N-/C-terminal extensions and an intact V3 loop (PDB 3JWD and 2B4C; blue) were fit into the SAXS density. D1D2 sCD4, which was cocrystallized with gp120 core, is shown in orange. (D) The V1/V2 loop structure from the complex with bNAb PG9 (PDB 3U4E; cyan spheres) occupies approximately the same volume as suggested by the SAXS shape reconstructions, although the specific conformation may be different. See also Movie S2 in the supplemental material.