title: Structure of the Varicella Zoster Virus Thymidylate Synthase Establishes Functional and Structural Similarities as the Human Enzyme and Potentiates Itself as a Target of Brivudine.
abstract: Varicella zoster virus (VZV) is a highly infectious human herpesvirus that is the causative agent for chicken pox and shingles. VZV encodes a functional thymidylate synthase (TS), which is the sole enzyme that produces dTMP from dUMP de novo. To study substrate binding, the complex structure of TSVZV with dUMP was determined to a resolution of 2.9 Å. In the absence of a folate co-substrate, dUMP binds in the conserved TS active site and is coordinated similarly as in the human encoded TS (TSHS) in an open conformation. The interactions between TSVZV with dUMP and a cofactor analog, raltitrexed, were also studied using differential scanning fluorimetry (DSF), suggesting that TSVZV binds dUMP and raltitrexed in a sequential binding mode like other TS. The DSF also revealed interactions between TSVZV and in vitro phosphorylated brivudine (BVDUP), a highly potent anti-herpesvirus drug against VZV infections. The binding of BVDUP to TSVZV was further confirmed by the complex structure of TSVZV and BVDUP solved at a resolution of 2.9 Å. BVDUP binds similarly as dUMP in the TSHS but it induces a closed conformation of the active site. The structure supports that the 5-bromovinyl substituent on BVDUP is likely to inhibit TSVZV by preventing the transfer of a methylene group from its cofactor and the subsequent formation of dTMP. The interactions between TSVZV and BVDUP are consistent with that TSVZV is indeed a target of brivudine in vivo. The work also provided the structural basis for rational design of more specific TSVZV inhibitors.
authors.affiliation: Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore.
authors.forename: Kelly
authors.initials: K
authors.lastname: Hew
authors.affiliation: Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore.
authors.forename: Sue-Li
authors.initials: SL
authors.lastname: Dahlroth
authors.affiliation: Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore.
authors.forename: Saranya
authors.initials: S
authors.lastname: Veerappan
authors.affiliation: Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore.
authors.forename: Lucy Xin
authors.initials: LX
authors.lastname: Pan
authors.affiliation: Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore.
authors.forename: Tobias
authors.initials: T
authors.lastname: Cornvik
authors.affiliation: Division of Structural Biology and Biochemistry, Nanyang Technological University, School of Biological Sciences, Singapore, Singapore.|Division of Biophysics, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.|Institute of Molecular and Cell Biology, Agency for Science, Technology and Research, Singapore, Singapore.
authors.forename: Pär
authors.initials: P
authors.lastname: Nordlund
mesh_terms: D000998:Antiviral Agents / Q000378:metabolism*; D001051:Apoenzymes / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D001973:Bromodeoxyuridine / Q000031:analogs & derivatives* / Q000378:metabolism; D014645:Herpesvirus 3, Human / Q000201:enzymology*; D006801:Humans; D008958:Models, Molecular; D010766:Phosphorylation; D011485:Protein Binding; D011487:Protein Conformation; D013940:Thymidylate Synthase / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D000998:Antiviral Agents; D001051:Apoenzymes; C020235:brivudine; D013940:Thymidylate Synthase; D001973:Bromodeoxyuridine