title: Single-step kinetics of HIV-1 reverse transcriptase mutants responsible for virus resistance to nucleoside inhibitors zidovudine and 3-TC.
abstract: Two mutants of HIV-1 reverse transcriptase (RT) associated with high-level resistance of the virus to AZT (RT-AZT: D67N, K70R, T215Y, K219Q, and M41L) or 3-TC (RT-3TC: M184V) were expressed in Escherichia coli and purified. None of these mutants showed significant changes in the affinity and kinetics of binding to a DNA/DNA primer/template. RT-AZT was investigated in detail with respect to its kinetics of incorporation of nucleotides. No change in the relative rates of TMP and AZTMP incorporation could be detected for RT-AZT with respect to wild type RT. These results imply that there is no increased discrimination against AZTTP in the mutant. This was found for DNA/DNA and DNA/RNA primer/template. Additionally, rapid kinetics of incorporation of 3'-amino-3'-deoxythymidine 5'-monophosphate (a possible metabolite of AZT) were investigated and compared with TMP incorporation, but no difference in its relative rates of incorporation between wild type RT and RT-AZT was detected. In contrast, the already very slow rate of incorporation of 3-TCMP seen with wild type enzyme was drastically reduced (by a factor of 23 and 36 with DNA/DNA primer/template and DNA/RNA primer/template, respectively) for RT-3TC, showing a clear correlation between in vitro and in vivo effects. The affinity of 3-TCTP to the RT-3TC-primer/template complex was not affected by the mutation M184V. A 1.6-fold cross-resistance to ddATP, the converted form of the prodrug ddI, could also be shown for RT-3TC, but no cross-resistance to ddCTP was detected. Additionally, rapid kinetics of AZTMP incorporation by RT-3TC were investigated. There was an indication of a slightly higher rate of incorporation of AZTMP by RT-3TC than wild type RT.
authors.affiliation: Max Planck Institut für molekulare Physiologie, Abteilung Physikalische Biochemie, Rheinlanddamm 201, D-44139 Dortmund, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Krebs
authors.forename: U
authors.initials: U
authors.lastname: Immendörfer
authors.forename: S H
authors.initials: SH
authors.lastname: Thrall
authors.forename: B M
authors.initials: BM
authors.lastname: Wöhrl
authors.forename: R S
authors.initials: RS
authors.lastname: Goody
mesh_terms: D019380:Anti-HIV Agents / Q000494:pharmacology; D004352:Drug Resistance, Microbial / Q000235:genetics; D054303:HIV Reverse Transcriptase / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000187:drug effects* / Q000201:enzymology; D007700:Kinetics; D019259:Lamivudine / Q000494:pharmacology*; D009154:Mutation; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology*; D015215:Zidovudine / Q000494:pharmacology*
chemical_list: D019380:Anti-HIV Agents; D018894:Reverse Transcriptase Inhibitors; D019259:Lamivudine; D015215:Zidovudine; D054303:HIV Reverse Transcriptase