The HIV envelope
glycoprotein gp120 plays a critical
role in virus entry and thus its
structure is of extreme interest for
the development of novel
therapeutics and vaccines. To
date, high resolution structural
information about gp120 in
complex with gp41 has proven
intractable. In this study we
characterize the structural
properties of gp120 in the
presence and absence of gp41
domains by NMR. Using the
peptide probe 12p1 (sequence =
RINNIPWSEAMM), which was
previously identified as an entry
inhibitor that binds to gp120, we
identify atoms of 12p1 in close
contact with gp120 in the
monomeric and trimeric states.
Interestingly the binding mode of
12p1 with gp120 is similar for
clades B and C. In addition, we
show a subtle difference in the
binding mode of 12p1 in the
presence of gp41 domains, i.e. the
trimeric state, which we interpret
as small differences in the gp120
structure in the presence of gp41