Abstract
The three enzyme forms (α-, αβ-, and β-form) of the RNA-dependent DNA polymerase (the reverse transcriptase) from three strains of avian sarcoma virus (ASV B 77, ASV
tsLA 334, and ASV QV 2) and one exogenous (avian myeloblastosis virus (AMV)) and one endogenous avian leukosis virus (Rous-associated virus type-0 (RAV-0)) were compared with each other in subunit structure and catalytic properties.
Despite the gross similarity in the subunit molecular weight (Mr(α)=65, 000 and Mr(β)=92, 000), minor differences were found in the molecular size of the subunit as determined by SDS-gel electrophoresis, the order being ASV
tsLA 334≤ASV QV 2<ASV B 77≤RAV-0=AMV. The structural differences were supported by analysis of peptide fragments after treatment with
S. aureus V 8 protease. Although the general catalytic properties of the purified enzymes from the five virus strains were similar, the selectivity of template-primer differed in the RAV-0 enzymes. The template-primer selectivity of the reverse transcriptases from all five virus strains tested was also found to be greatly influenced by the reaction temperature for DNA synthesis, resulting in a temperature-dependent increase of poly (dG) synthesis over [(A)
n]•[(dT)
12-18]-dependent poly (dT) synthesis. The RAV-0 enzymes required a lower temperature for DNA synthesis, particularly for [(C)
n]•[(dG)
12-18]-dependent poly (dG) synthesis.
