Homodimeric reverse transcriptases from Rous sarcoma virus mutated within the polymerase or RNase H active site of one subunit are active

Abstract

Heterodimeric reverse transcriptase (RT) αβ from Rous sarcoma virus (RSV) possesses an asymmetric subunit organization with the polymerase and RNase H active sites localized in the α subunit. To determine whether homodimeric RSV RTs α (63 kDa) or β (95 kDa) assume α subunit organization similar to that of the heterodimer, an essential aspartic acid residue was mutated in the active site of either the polymerase (Asp181 > Asn) or the RNase H (Asp505 > Asn). Homodimeric α or β RT consisting of one wild-type and one mutated subunit exhibit polymerase or RNase H activity, respectively, whereas the corresponding doubly mutated enzymes are inactive, indicating that the catalytic sites of the polymerase and RNase H domains are formed by only one subunit of the homodimer.