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: Kelly Hew, Sue-Li Dahlroth, Saranya Veerappan, Lucy Xin Pan, Tobias Cornvik, Pär Nordlund
• Journal: PloS one (PLoS One) Vol. 10 Issue 12 Pg. e0143947 ( 2015) ISSN: 1932-6203 [Electronic] United States
• PMID: 26630264 (Publication Type: Journal Article)

Chemical References

• Antiviral Agents
• Apoenzymes
• brivudine
• Thymidylate Synthase
• Bromodeoxyuridine

Topics

• Antiviral Agents (metabolism)
• Apoenzymes (chemistry, metabolism)
• Binding Sites
• Bromodeoxyuridine (analogs & derivatives, metabolism)
• Herpesvirus 3, Human (enzymology)
• Humans
• Models, Molecular
• Phosphorylation
• Protein Binding
• Protein Conformation
• Thymidylate Synthase (chemistry, metabolism)