An orthogonal single-molecule experiment reveals multiple-attempt dynamics of type IA topoisomerases

Kathryn H. Gunn, John F. Marko, Alfonso Mondragón*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Topoisomerases are enzymes that are involved in maintaining the topological state of cellular DNA. Their dynamic characteristics remain poorly understood despite numerous structural, biophysical and biochemical studies. Recent single-molecule experiments revealed that an important feature of the type IA topoisomerase mechanism is the presence of pauses between relaxation events. However, these experiments could not determine whether the protein remains DNA bound during the pauses or what relationship may exist between protein domain movements and topological changes in the DNA. By combining two orthogonal single-molecule techniques, we found that E. coli topoisomerase I constantly changes conformation when attempting to modify the topology of DNA, but succeeds in only a fraction of the attempts. Thus, its mechanism can be described as a series of DNA strand-passage attempts that culminate in a successful relaxation event.

Original languageEnglish (US)
Pages (from-to)484-490
Number of pages7
JournalNature Structural and Molecular Biology
Issue number5
StatePublished - May 4 2017

ASJC Scopus subject areas

  • Molecular Biology
  • Structural Biology


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