(A) Construction of recombinant gp120 fragments. The
relative position of the four β strands, β2, β3, β20, and
β21, is indicated in the schematic presentation of gp120. A glycine
residue was added to MBri between β21 and β2 as a linker to join
two gp120 fragments that span from amino acids 421–437 and 118–207 as
indicated (437G118). The amino acid numbering system used here is the
same as that described by Kwong et al. (22). M2–MBri is
identical to MBri, except for an amino acid change that corresponds to
the T198P mutation (* under the β3 region indicates this
mutation). DP283 is a DH012 V3 peptide. (B). Reactivity
of IgGb12 to recombinant gp120 fragments. The binding of IgGb12 to the
recombinant proteins was determined by using an ELISA assay as
described (25). IgGb12 (10 μg/ml) was added to ELISA plates coated
with the recombinant proteins MBri or M2–MBri in the presence of
various concentrations of the free MBri or M2–MBri, respectively, as
indicated.