Figure 1.

Structure of envelope chimeras. Wild-type and chimeric envelope proteins were expressed either in the context of the pCR3.1 plasmid or in an HIV-1 proviral context. Chimeric env genes were constructed by using the indicated restriction enzyme sites in the gp120 coding region. By using coordinates based on the 504 amino acid (aa) ADA gp120 protein, we inserted the following ADA envelope sequences into the BaL envelope: A_1–5/B, aa 1–473; A_3–5/B, aa 284–473; A₃/B, aa 284–359; A_1–2/B, aa 42–284; A₁/B, aa 42–145; and A₂/B, aa 145–284. All other chimeras substituted equivalent env sequences with the exception of IIIB/V3-BaL, which has been described previously (18). J, junction between gp120 and gp41.