<p>This domain is known as the thumb domain. It is composed of a four helix bundle [<cite idref="PUB00012846"/>]. Reverse transcriptase converts the viral RNA genome into double-stranded viral DNA. Reverse transcriptase often occurs in a polyprotein; with integrase, ribonuclease H and/or protease, which is cleaved before the enzyme takes action. The impact of antiretroviral treatment on the first 400 amino acids of HIV reverse transcriptase is good. Little is known, however, of the antiretroviral drug impact on the C-terminal domains of Pol, which includes the thumb, connection and RNase H [<cite idref="PUB00043354"/>]. Evidence suggests that these might be well conserved domains.</p>