Figure 3.

Structural organization and proteolytic processing of reverse transcriptase and integrase. A: The precursor Gag-Pol protein is processed by the viral protease into an intermediate polyprotein. The avian polyprotein exists as a dimer of the β subunit that is processed into the active αβ subunits (RT) and integrase (IN). The α subunit contains the active polymerase and RNaseH sites while β retains IN residues. RT does not possess integration capabilities; B: Cleavage of the human immunodeficiency virus (HIV) polyprotein produces the active dimeric RT and IN. The HIV p66 subunit possesses the polymerase and RNaseH active sites. RT: Reverse transcriptase.