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Prolonged treatment of AIDS patients with azidothymidine results in the development of resistance to the drug which correlates with the appearance of point mutations in the reverse transcriptase (RT) coding region within the HIV-1 pol gene. Kinetic studies of interactions of wild type RT and its mutants harbouring the above mutations with substrates and azidothymidine 5'-triphosphate (AZTTP) have been carried out. The complete mutant containing all the above described mutations possess the highest resistance on all the templates tested. Significant increases in resistance for mutants 67,70,215 and 67,215 on all the templates have also been observed. Inhibition of mutant enzymes by AZTTP depends on the template used.

Prolonged therapy of AIDS patients with azidothymidine results in the development of resistance to the drug. This phenomenon is accompanied by the appearance of point mutations in the pol gene coding for reverse transcriptase (RT). Kinetic studies of interactions of wild type RT and its forms containing the above-mentioned mutations with substrates and azidothymidine 5'-triphosphate have been carried out. Considerable differences in the affinities of RT and the mutants for RNA and DNA heteropolymer templates were established. The mutations did not affect the RT affinity for dNTP; however, its location influenced considerably the inhibition of the reaction with azidothymidine 5'-triphosphate.

Monomeric DNA and RNA polymerases contain a number of conserved motifs. By means of random and oligonucleotide-directed mutagenesis the point mutants of bacteriophage T7 RNA polymerase containing the amino acid substitutions in motif B which is the part of the active site were obtained. The kinetic properties of the mutants were studied. The results obtained suggest that amino acid residues 636, 639 and 646 are involved in the binding of the initiating GTP, the selection of correct nucleoside triphosphate and interaction with the promoter, respectively.