Crystal structure of chemically synthesized HIV-1 protease and a ketomethylene isostere inhibitor based on the p2/NC cleavage site

Here we report the X-ray structures of chemically synthesized HIV-1 protease and the inactive [D25N]HIV-1 protease complexed with the ketomethylene isostere inhibitor Ac–Thr–Ile–Nleψ[CO–CH2]Nle–Gln–Arg.amide at 1.4 and 1.8 Å resolution, respectively. In complex with the active enzyme, the keto-group was found to be converted into the hydrated gem-diol, while the structure of the complex with the inactive D25N enzyme revealed an intact keto-group. These data support the general acid–general base mechanism for HIV-1 protease catalysis.