Fine characterization of the antigenic site within the flap region in the protease protein of HIV-1

The aspartate protease encoded by human immunodeficiency virus type 1 is es sential for cleavage of the gag and gag-pol precursor proteins. The majorit y of HIV-1-antibody-positive sera react with the protease. In this study we used a substitution set of peptides for detailed characterization of the e arlier defined antigenic site (aa 44-58) within the central "flap" region, also important in the context of conformational flexibility during protease inhibitor binding. We found that isoleucine at position 54 was important f or creating an antigenic site required for binding of anti-HIV-1 sera. The identification of structurally essential amino acids in the flap region of HIV-1 PR may have important implications in future development of antiviral drugs.