Extended Data Fig. 2: Binding of PGT151 stabilizes a state-2-like conformational state of HIV-1 Env.

a, Structure of HIV-1_JR-FL Env(ΔCT) in complex with PGT151¹⁹. Two PGT151 antigen-binding fragments are distant from the positions of the gp120 variable loops (V1 and V4) that carry the fluorophores. b, Population FRET histograms of unliganded HIV-1_JR-FL Env(ΔCT), and HIV-1_JR-FL Env(ΔCT) in the presence of 10 μg ml⁻¹ sCD4_D1D2–Igαtp. c–f, Addition of PGT151 at neutralizing concentrations (10 μg ml⁻¹) shifts the conformational landscapes for enzymatically labelled HIV-1_JR-FL (c, e) and HIV-1_BG505 (d, f) from the unliganded preference towards state 1 (red solid lines) to a preference for state 2 (blue solid lines). g, The addition of PGT151 to BG505 sgp140 SOSIP.664 did not alter the dominance of the state-2-like conformation exhibited in the absence of PGT151. h, Schematic of use of amber-suppressor tRNAs to introduce unnatural amino acids that can be clicked with fluorophores (h, top; see Methods), and schematic comparison between the Q3 and A1 double tag used for enzymatically labelling and click-labelling of V1 and V4 of HIV-1_JR-FL (h, middle) and HIV-1_BG505 Env (h, bottom). To introduce the unnatural amino acid TCO*, Asn136 in the V1 loop of HIV-1_JR-FL or Ser401 in the V4 loop of HIV-1_BG505 was genetically altered to an amber (TAG) stop codon. i–l, Experiment as in c–f, characterizing the conformational landscape upon binding of PGT151 to click-labelled HIV-1_JR-FL V1–Asn136_TAG V4–A1 (i, k), and HIV-1_BG505 V1–Q3 V4–Ser401_TAG (j, l). Neutralization data (mean ± s.d.) are averaged from three independent experiments in triplicates (c, d, i, j). FRET population histograms represent mean ± s.e.m., determined from three independent populations of smFRET traces.