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Figure 2.
View larger version (50K): [in
this window] [in
a new window] Fig. 2. Epitopes, bound conformations, and
trimer modeling. (A) Epitope hydrophobicity. The surface of
gp120 is shown in gray, with hydrophobic residues highlighted in
green. Binding surfaces for CD4, F105, b12, and b13 are outlined
in orange. (B) Ligand-bound conformation of gp120. Polypeptides
of gp120 are depicted in ribbon representation with inner
domains shown in light gray, outer domains in dark gray, and
regions that in the CD4-bound state correspond to the bridging
sheet shown in red. Residues 109 and 428 are highlighted in blue
and shown in stick representation. (C) Viral spike
compatibility. Density maps derived from the cryo–electron
tomography of HIV-1 BaL isolate spike are shown in gray for CD4
and 17b- and b12-bound states (first and third from left,
respectively), along with optimal fits of atomic-level models
(30). To model F105- and b13-bound forms of gp120 into likely
viral spike orientations, the invariant β-sandwich of the gp120
inner domain was superimposed. Likely clashes of V1/V2 in the
superimposed conformation with neighboring protomers close to
the trimer axis are highlighted in light blue.
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