Probing the HIV GP120 Envelope Glycoprotein Conformation by NMR

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.