title: The sugar ring of the nucleoside is required for productive substrate positioning in the active site of human deoxycytidine kinase (dCK): implications for the development of dCK-activated acyclic guanine analogues.
abstract: The low toxicity of acyclovir (ACV) is mainly due to the fact that human nucleoside kinases have undetectable phosphorylation rates with this acyclic guanine analogue. In contrast, herpes virus thymidine kinase (HSV1-TK) readily activates ACV. We wanted to understand why human deoxycytidine kinase (dCK), which is related to HSV1-TK and phosphorylates deoxyguanosine, does not accept acyclic guanine analogues as substrates. Therefore, we crystallized dCK in complex with ACV at the nucleoside phosphoryl acceptor site and UDP at the phosphoryl donor site. The structure reveals that while ACV does bind at the dCK active site, it does so adopting a nonproductive conformation. Despite binding ACV, the enzyme remains in the open, inactive state. In comparison to ACV binding to HSV1-TK, in dCK, the nucleoside base adopts a different orientation related by about a 60 degrees rotation. Our analysis suggests that dCK would phosphorylate acyclic guanine analogues if they can induce a similar rotation.
authors.affiliation: Department of Biochemistry and Molecular Genetics University of Illinois at Chicago, Chicago, Illinois 60607, USA.
authors.forename: Saugata
authors.initials: S
authors.lastname: Hazra
authors.forename: Manfred
authors.initials: M
authors.lastname: Konrad
authors.forename: Arnon
authors.initials: A
authors.lastname: Lavie
mesh_terms: D000212:Acyclovir / Q000737:chemistry; D000595:Amino Acid Sequence; D000998:Antiviral Agents / Q000737:chemistry; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003842:Deoxycytidine Kinase / Q000737:chemistry*; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry*; D006564:Herpesviridae / Q000201:enzymology; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009705:Nucleosides / Q000737:chemistry*; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D013937:Thymidine Kinase / Q000737:chemistry; D014530:Uridine Diphosphate / Q000737:chemistry
chemical_list: D000998:Antiviral Agents; D009705:Nucleosides; D014530:Uridine Diphosphate; D006147:Guanine; D013937:Thymidine Kinase; C092717:thymidine kinase 1; D003842:Deoxycytidine Kinase; D000212:Acyclovir