HIV protease is responsible for processing of the gag and gag-pol polyproteins during virion
maturation. The activity of this enzyme is essential for virus infectivity, rendering the protein a
major therapeutic target for AIDS treatment. This articles reviews the biochemical and
biophysical properties of the enzyme. The clinical and in vitro observations of resistance to
protease inhibitors are discussed from the perspective of drug resistance mechanisms of
HIV protease mutants.