DNA binding induces conformational transition within human DNA topoisomerase I in solution
Related Experiment Video
Updated: Sep 29, 2026

CD Spectroscopy to Study DNA-Protein Interactions
Published on: February 10, 2022
Vladimir Oleinikov1, Alyona Sukhanova, Konstantin Mochalov
1EA3306, Institut Fédératif de Recherche 53 Biomolécules, UFR de Pharmacie, Université de Reims Champagne-Ardenne, 51 Rue Cognacq Jay, 51100 Reims, France.
Abstract:
We employed Raman and circular dichroism (CD) spectroscopy to probe the molecular structure of 68-kDa recombinant human DNA topoisomerase I (TopoI) in solution, in a complex with a 16-bp DNA fragment containing a camptothecin-enhanced TopoI cleavage site, and in a ternary complex with this oligonucleotide and topotecan. Raman spectroscopy reveals a TopoI secondary structure transition and significant changes in the hydrogen bonding of the tyrosine residues induced by the DNA binding. CD spectroscopy confirms the Raman data and identifies a DNA-induced (>7%) decrease of the TopoI alpha helix accompanied by at least a 6% increase of the beta structure. The Raman DNA molecular signatures demonstrated a bandshift that is expected for a net change in the environment of guanine C6 [double bond] O groups from pairing to solvent exposure. The formation of a ternary cleavage complex with TopoI, DNA, and topotecan as probed by CD spectroscopy reveals neither additional modifications of the TopoI secondary structure nor of the oligonucleotide structure, compared to the TopoI-oligonucleotide complex.
Related Concept Videos
DNA Topoisomerases
Types and Mechanism of action
Topoisomerases are divided into two main types. Type I...
Single-Strand DNA Binding Proteins
DNA Helicases
Cooperative Binding of Transcription Regulators
Nucleosome Remodeling
Nucleosome remodeling complex
Eukaryotic cells have specialized enzymes called ATP-dependent nucleosome remodeling enzymes. These enzymes...
The Nucleosome
In a chromosome, DNA is wound twice around a protein complex called a histone octamer core, which consists of 8 histone proteins. This...

