Fig. 6
BG18 contacts with gp120 V1-loop. a Surface and cartoon representation of BG18 VH (dark blue) and VL (light blue) loops involved in gp120 V1-loop (gray; residues 128–158, disordered residues depicted as dashed red line) interactions. Electron density contoured at 1σ from a 2Fobs−Fcalc composite annealed omit map is shown (gray mesh). Glycans at position N133gp120 and N156gp120 are shown. b Cartoon and stick representation of residue interactions between BG18 VL domain (light blue) and the gp120 V1-loop (gray). Potential H-bonding occurs between T139gp120 and BG18 T30LC in the CDRL1 loop. In addition, BG18 W67LC in FWRL3 stacks against I138gp120. BG18 contacts with gp120 positions 138 and 139 are likely specific to Envs with V1 characteristics similar to BG505, since similar conformations were not observed in our BG18-B41 structure. H-bonds and pi-stacking are indicated by black dashed lines. Red asterisk on N137gp120 indicates a PNGS. c Electrostatic surface potentials with red indicating negative electrostatic potential and blue indicating positive electrostatic potential for BG18 shown with cartoon and stick representation of nearby gp120 elements. BG18 includes a positively charged cleft in the vicinity of the gp120 V1-loop (dashed line indicates disordered region), which may provide increased protein–protein interactions with the gp120 surface in HIV-1 strains harboring charged residues in the V1-loop
