FIG. 5.

Comparison of the abilities of the various HIV-1 RTs (mutant and wild-type [WT]) to excise AZTMP from the end of the primer and extend the primer in the presence of AZTTP and various concentrations of ATP. The primer is fully blocked with AZTMP at the beginning of the reaction (see Materials and Methods). A short (25 nucleotides long) template extension provides an additional opportunity for the enzymes to incorporate AZTTP and excise AZTMP. The assay measures the percentage of the primer that is completely extended by each enzyme at various ATP concentrations. (A) Results obtained at low concentrations (10 μM) of each of the four dNTPs. (B) Results obtained with high concentrations (100 μM) of each of the four dNTPs.