Efficiency of excision of incorporated ZDV-MP in the presence of 3.5 mM ATP. The efficiencies of the reactions with wild-type and mutant RTs were compared in time course experiments. (A) Graphic representation of the cell-free system (PPT-57/PPT-18) used to monitor the excision of ZDV-MP from newly synthesized HIV-1 DNA. (B) Comparison between wild-type RT and L74V RT. (C) Comparison between M184V RT and the double mutant L74V/M184V RT. Lane C corresponds to control labeled primer. Lanes 1 to 11 show reaction products at 0, 1, 3, 6, 10, 15, 22, 30, 45, 60, and 90 min after addition of the excision mix, respectively. (D) Graphic representation of gel-based assays shown in B and C. Values are means of at least three independent experiments ± standard error.