An inducible HIV type 1 gp41 HR-2 peptide-binding site on HIV type 1 envelope gp120.

Synthetic peptides of sequences within the HIV-1 gp41 heptad repeat-regions (HR-1 and HR-2) can effectively inhibit cell fusion and viral entry. DP178 (T-20), an HR-2 peptide, acts by inhibiting the association between HR-1 and HR-2, thereby interfering with HIV-1 fusion and viral entry. HR-2 peptide binding is predicted to be an important indicator of the presence of Env gp41 fusion intermediate conformation.