title: Azidodeoxythymidine and didehydrodeoxythymidine as inhibitors and substrates of the human herpesvirus 8 thymidine kinase.
abstract: Human herpesvirus 8 (HHV-8), the aetiological agent of Kaposi's sarcoma (KS), encodes many core genes that have been maintained during evolution of the Herpesviridae. Among these is a thymidine kinase (TK) homologue (ORF21), which has 12% homology to the related TK encoded by herpes simplex virus. We show that the HHV-8 TK is a functional deoxythymidine (dT) kinase, with Michaelis constants (K(m)) for dT and ATP of 18.5 and 6.6 microM, respectively. Using homology modelling coupled with site-directed mutagenesis, we identify Gly265, Asp362 and Phe372 as key amino acid residues involved in the catalytic process. The HHV-8 TK is competitively inhibited by azidodeoxythymidine (zidovudine) and didehydrodeoxythymidine (stavudine) and can also accept these anti-retroviral compounds as substrates. These data have implications for our understanding of changes in AIDS-KS incidence following the clinical licensing of these compounds and in the development of new therapies for KS.
authors.affiliation: Department of Virology, Royal Free and University College Medical School, University College London, Royal Free Campus, Rowland Hill Street, Hampstead, London NW3 2PF, UK.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Lock
authors.forename: Nicola
authors.initials: N
authors.lastname: Thorley
authors.forename: Jeanette
authors.initials: J
authors.lastname: Teo
authors.forename: Vincent C
authors.initials: VC
authors.lastname: Emery
mesh_terms: D000595:Amino Acid Sequence; D019380:Anti-HIV Agents / Q000378:metabolism / Q000494:pharmacology; D020134:Catalytic Domain / Q000235:genetics; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D019288:Herpesvirus 8, Human / Q000187:drug effects* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D007700:Kinetics; D008297:Male; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D018119:Stavudine / Q000378:metabolism / Q000494:pharmacology*; D013379:Substrate Specificity; D013937:Thymidine Kinase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015215:Zidovudine / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D019380:Anti-HIV Agents; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D015215:Zidovudine; D018119:Stavudine; D013937:Thymidine Kinase