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Protein unfolding in drug-RNase complexes
J F Neault1, S Diamantoglou, M Beauregard
1Department of Chemistry-Biology, University of Québec at Trois-Rivières, Canada G9A 5H7.
Journal of Biomolecular Structure & Dynamics
|December 21, 2007
Summary
This study compares how drugs like AZT, cis-Pt, aspirin, and vitamin C affect bovine pancreatic ribonuclease A (RNase A) stability and structure. Spectroscopic analysis reveals significant protein unfolding and conformational changes upon drug binding, impacting RNase A activity.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Bovine pancreatic ribonuclease A (RNase A) is an enzyme that cleaves RNA.
- RNase A possesses binding sites for various organic and inorganic molecules.
- Ligand binding can modulate RNase A's secondary structure and catalytic function.
Purpose of the Study:
- To investigate the effects of AZT (anti-AIDS), cis-Pt (antitumor), aspirin (anti-inflammatory), and vitamin C (antioxidant) on RNase A stability and conformation.
- To compare the binding affinities and structural impacts of these diverse drug molecules on RNase A in vitro.
Main Methods:
- UV-visible spectroscopy
- Fourier-transform infrared (FTIR) spectroscopy
- Circular dichroism (CD) spectroscopy
Main Results:
- Binding affinities were determined for each drug-RNase A complex: KAZT=5.29x10(4) M(-1), Kaspirin=3.57x10(4) M(-1), Kcis-Pt=5.66x10(3) M(-1), and Kascorbate=3.50x10(3) M(-1).
- Aspirin, vitamin C, and cis-Pt induced major protein unfolding, decreasing alpha-helix content from 29% to 20% and increasing beta-sheet content from 39% to 45%.
- AZT binding resulted in a minor increase in alpha-helix content.
Conclusions:
- The binding of AZT, cis-Pt, aspirin, and vitamin C significantly alters the secondary structure and stability of RNase A.
- These conformational changes suggest potential modulation of RNase A's catalytic activity by these therapeutic agents.
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