Electron Paramagnetic Resonance (EPR) Study of Spin-Labeled Camptothecin Derivatives: A Different Look of the Ternary Complex
Citations Over Time
Abstract
Camptothecin (CPT) derivatives are clinically effective poisons of DNA topoisomerase I (Top1) able to form a ternary complex with the Top1-DNA complex. The aim of this investigation was to examine the dynamic aspects of the ternary complex formation by means of site-directed spin labeling electron paramagnetic resonance (SDSL-EPR). Two semisynthetic CPT derivatives bearing the paramagnetic moiety were synthesized, and their biological activity was tested. A 22-mer DNA oligonucleotide sequence with high affinity cleavage site for Top1 was also synthesized. EPR experiments were carried out on modified CPT in the presence of DNA, of Top1, or of both. In the last case, a slow motion component in the EPR signal appeared, indicating the formation of the ternary complex. Deconvolution of the EPR spectrum allowed to obtain the relative drug amounts in the complex. It was also possible to demonstrate that the residence time of CPT "trapped" in the ternary complex is longer than hundreds of microseconds.
Related Papers
- → Nitroxide spin labels and EPR spectroscopy: A powerful association for protein dynamics studies(2021)105 cited
- → Structural Dynamics of Protein Interactions Using Site-Directed Spin Labeling of Cysteines to Measure Distances and Rotational Dynamics with EPR Spectroscopy(2023)7 cited
- → Distance Measurements by Continuous Wave EPR Spectroscopy to Monitor Protein Folding(2011)16 cited
- → EPR Spectra of Spin-Labeled OmpA Reflect Both Protein Dynamics and Label Configuration in Membrane Mimetic Systems(2011)
- Application of site-directed spin labeling combined with electron paramagnetic resonance to protein structure studies(2006)