The protease is located into the core of the mature virus particle.. As the virus is assembled, the Gag and Gag/pol polyproteins are incorporated along with the RNA and other proteins. The virus then buds but at least at the time of budding it is not infectious. Further conformational changes must occur in viral proteins for infectivity to be gained. During the maturation process, the Gal/pol polyprotein is cut by the protease to produce MA., CA, NC and p6 from Gag and PR, RT and In from pol. Note the virus makes about 20 times as much gag as gag/pol polyprotein. The gag and pol genes are in different reading frames yet a continuous protein si made. Happens because there is a secondary structure at the interface between the two genes that causes ribosomal frame shifting. Such frame shifting occurs about 5% of the time leading to the extension of the gag protein into the pol protein. The protease is a dimer but it must initially cut itself free and work as part of the gag/pol protein (autoprocessing which is influenced by the p6 protein Cleavage efficiency differs with the site to be cut and this influences, the order of the appearance of proteins. There is a spacer peptide (p2) between the CA and NC proteins that may control cleavage efficiency. It appears that rate of processing during maturation is important since over expression of the protease leads to altered processing and reduced infectivity. The active site of the enzyme is formed by the dimer, both monomers contributing one catalytically essential aspartic acid. The protease is similar to other aspartyl proteases.

For further information see: Alan Frankel and John A. T. Young, HIV-1: Fifteen proteins and an RNA Annual Review of Biochemistry 67: 1-25, 1998