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AZT binding to Na,K-ATPase
A Ahmed-Ouameur1, J-F Neault, S Claveau
1Department of Chemistry-Biology, University of Québec at Trois-Riviéres, C.P. 500, TR (Québec) Canada G9A 5H7.
Cell Biochemistry and Biophysics
|January 28, 2005
Summary
3'-azido-3'-deoxythymidine (AZT), an HIV drug, interacts with Na,K-ATPase. At low concentrations, AZT binds via hydrogen bonds, while higher concentrations form AZT-lipid complexes, causing minor protein structure changes.
Area of Science:
- Biochemistry
- Structural Biology
- Pharmacology
Background:
- 3'-azido-3'-deoxythymidine (AZT) is a primary drug for treating human immunodeficiency virus (HIV).
- Drug interactions with DNA and proteins are crucial for understanding its in vivo mechanism of action.
Purpose of the Study:
- To investigate the interaction between AZT and Na,K-ATPase.
- To characterize the binding mode, binding constants, and effects on protein secondary structure.
Main Methods:
- Utilized ultraviolet absorption and Fourier transform infrared (FTIR) difference spectroscopy.
- Employed self-deconvolution, second-derivative resolution enhancement, and curve-fitting techniques.
- Studied interactions in both H2O and D2O solutions at physiological pH.
Main Results:
- At low AZT concentrations (0.1 microM), hydrogen bonding occurred with polypeptide C=O and C-N groups, yielding binding constants K1 = 5.3 x 10(5) M(-1) and K2 = 9.8 x 10(3) M(-1).
- Higher AZT concentrations promoted AZT-lipid complex formation.
- Minor alterations in protein secondary structure were observed at high AZT concentrations (1 mM), with changes in alpha-helix, beta-pleated, turn, beta-antiparallel, and random coil percentages.
Conclusions:
- AZT exhibits concentration-dependent binding interactions with Na,K-ATPase.
- These interactions involve hydrogen bonding at low concentrations and complex formation at high concentrations, leading to subtle modifications in protein secondary structure.