Abstract
We have used a broad range of spectroscopic and viscometric techniques to demonstrate that the complexation of a cytotoxic, topoisomerase I-poisoning terbenzimidazole (5PTB) with the poly(dA)•poly(dT) duplex exhibits properties characteristic of both intercalation and minor groove binding. Our results reveal the following features: (i) Optical melting profiles reveal that 5PTB binding enhances the thermal stability of the poly(dA)• poly(dT) duplex; (ii) Fluorescence-detected 5PTB binding to the poly(dA)•poly(dT) duplex reveals four apparent "site sizes," ranging from 1 to 13 base pairs (bp) per bound drug; (iii) Flow linear dichroism data suggest conformational heterogeneity among the poly(dA)•poly(dT)-bound 5PTB molecules, with substantial contributions from drug molecules bound in the minor groove; (iv) Fluorescence resonance energy transfer data reveal properties characteristic of a significant contribution from an intercalative mode of binding; (v) Viscometric, fluorescence quenching, and netropsin competition data are consistent with 5PTB binding to poly(dA)•poly(dT) by "mixed" modes, which are operationally defined as single or multiple binding populations that individually and/or collectively express both intercalative and minor groove binding properties. We comment on a potential correlation between drugs that exhibit such "mixed" mode binding motifs and those that express antineoplastic activity through inhibition of topoisomerase I.
Original language | English |
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Pages (from-to) | 115-133 |
Number of pages | 19 |
Journal | Drug Design and Discovery |
Volume | 13 |
Issue number | 3-4 |
Publication status | Published - 1996 |
Externally published | Yes |
Keywords
- DNA base-drug resonance energy transfer
- Flow linear dichroism
- Fluorescence quenching
- Förster critical distance
- Mixed mode DNA binding
ASJC Scopus subject areas
- Molecular Medicine
- Drug Discovery