Analogues of vaccinia virus DNA topoisomerase I modified at the active site tyrosine

Rong Gao, Yi Zhang, Ambar K. Choudhury, Larisa M. Dedkova, Sidney M. Hecht

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


The mechanism of type IB topoisomerase-mediated DNA relaxation was studied by modification of vaccinia topoisomerase I at the active site tyrosine (position 274) with several tyrosine analogues. These analogues had varied steric, electronic, and stereochemical features to permit assessment of those structural elements required to support topoisomerase function. Eleven tyrosine analogues were successfully incorporated into the active site of vaccinia topoisomerase I. It was found that only tyrosine analogues having the phenolic -OH group in the normal position relative to the protein backbone were active. Modifications that replaced the nucleophilic tyrosine OH (pKa ≈ = 10.0) group with NH2 (pKa 4.6), SH (pKa ≈ 7.0), or I groups or that changed the orientation of the nucleophilic OH group essentially eliminated topoisomerase I function. For the active analogues, the electronic effects and H-bonding characteristics of substituents in the meta-position of the aromatic ring may be important in modulating topoisomerase I function. The pH profile for the functional analogues revealed a small shift toward lower pH when compared with wild-type topoisomerase I.

Original languageEnglish (US)
Pages (from-to)3321-3331
Number of pages11
JournalJournal of the American Chemical Society
Issue number10
StatePublished - Mar 16 2005
Externally publishedYes

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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