title: Different patterns of inhibition of avian myeloblastosis virus reverse transcriptase activity by 3'-azido-3'-deoxythymidine 5'-triphosphate and its threo isomer.
abstract: The two isomers 3'-azido-3'-deoxythymidine 5'-triphosphate (erythro-AZT-TP) and 1-(3'-azido-2',3'-dideoxy-beta-D-xylofuranosyl)thymine 5'-triphosphate (threo-AZT-TP) were studied as inhibitors of the reverse transcriptase activity of avian myelobastosis virus. Kinetic analysis of the (rA)n X (dT)12-18 (a standard template primer complex of polyriboadenylate and oligodeoxythymidylate of indicated length)-directed reaction revealed that erythro-AZT-TP was a competitive inhibitor with respect to dTTP, whereas threo-AZT-TP was a noncompetitive inhibitor. The apparent Ki values, as calculated from Dixon plots, were 0.48 and 5.5 microM, respectively, compared with a Km value for dTTP of about 70 microM. These results indicate that erythro-AZT-TP had an approximately 150-times-higher affinity to the enzyme than dTTP had and that the avian myeloblastosis virus reverse transcriptase had different binding sites for the two isomers.
mesh_terms: D001354:Avian Leukosis Virus / Q000201:enzymology*; D009189:Avian Myeloblastosis Virus / Q000201:enzymology*; D001667:Binding, Competitive; D054306:Dideoxynucleotides; D007536:Isomerism; D018894:Reverse Transcriptase Inhibitors; D013942:Thymine Nucleotides / Q000378:metabolism / Q000494:pharmacology*; D014764:Viral Proteins / Q000037:antagonists & inhibitors*; D015215:Zidovudine / Q000031:analogs & derivatives*
chemical_list: D054306:Dideoxynucleotides; D018894:Reverse Transcriptase Inhibitors; D013942:Thymine Nucleotides; D014764:Viral Proteins; D015215:Zidovudine; C052873:zidovudine triphosphate; C024157:thymidine 5'-triphosphate