Kinetics of inhibition of HIV type 1 reverse transcriptase-bearing NRTI-associated mutations by apricitabine triphosphate.
We wished to investigate the effects of various mutations in HIV-1 reverse transcriptase (RT) on biochemical inhibition by the active form of a novel nucleoside termed apricitabine. Accordingly, we studied the efficiency of chain-termination mediated by apricitabine triphosphate (TP) in cell-free assays that used either recombinant wild-type or mutated RTs. We also performed steady-state-kinetics and primer-unblocking assays. Subtype C RTs were also analysed. The results showed that the K65R mutation in RT caused reductions in the efficiency of chain-termination of apricitabine-TP by increasing its Ki. However, K65R did not affect rates of primer unblocking for apricitabine-TP. No significant differences were found between subtype C and subtype B RTs with regard to any of the parameters studied. Other mutations such as M184V, L74V and K103N had no effect on the efficiency of chain termination by apricitabine-TP. Thus, the mechanism of reduced susceptibility to apricitabine of viruses containing K65R in RT seems to be mediated exclusively through a reduction in binding or incorporation of apricitabine-TP. Unlike some other nucleoside analogues, increased excision of incorporated apricitabine does not seem to be a cause of resistance to apricitabine.
Frankel
Fernando A
FA
McGill AIDS Centre, Lady Davis Institute-Jewish General Hospital, Montreal, Quebec, Canada.
Coutsinos
Dimitrios
D
Xu
Hongtao
H
Wainberg
Mark A
MA
D000595:Amino Acid Sequence; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D054303:HIV Reverse Transcriptase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics*; D007700:Kinetics; D008969:Molecular Sequence Data; D009154:Mutation; D018894:Reverse Transcriptase Inhibitors / Q000494:pharmacology*
D018894:Reverse Transcriptase Inhibitors; D003841:Deoxycytidine; D054303:HIV Reverse Transcriptase; C508042:apricitabine