Importance of the Fourth Alpha-Helix within the CAP Homology Domain of Type II Topoisomerase for DNA Cleavage Site Recognition and Quinolone Action
AUTOR(ES)
Strumberg, Dirk
FONTE
American Society for Microbiology
RESUMO
We report that point mutations causing alteration of the fourth alpha-helix (α4-helix) of the CAP homology domain of eukaryotic (Saccharomyces cerevisiae) type II topoisomerases (Ser740Trp, Gln743Pro, and Thr744Pro) change the selection of type II topoisomerase-mediated DNA cleavage sites promoted by Ca2+ or produced by etoposide, the fluoroquinolone CP-115,953, or mitoxantrone. By contrast, Thr744Ala substitution had minimal effect on Ca2+- and drug-stimulated DNA cleavage sites, indicating the selectivity of single amino acid substitutions within the α4-helix on type II topoisomerase-mediated DNA cleavage. The equivalent mutation in the gene for Escherichia coli gyrase causing Ser83Trp also changed the DNA cleavage pattern generated by Ca2+ or quinolones. Finally, Thr744Pro substitution in the yeast type II topoisomerase rendered the enzyme sensitive to antibacterial quinolones. This study shows that the α4-helix within the conserved CAP homology domain of type II topoisomerases is critical for selecting the sites of DNA cleavage. It also demonstrates that selective amino acid residues in the α4-helix are important in determining the activity and possibly the binding of quinolones to the topoisomerase II-DNA complexes.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=127396Documentos Relacionados
- A cluster of basic amino acids within an alpha-helix is essential for alpha-subunit recognition by the glycoprotein hormone N-acetylgalactosaminyltransferase.
- beta-Endorphin: formation of alpha-helix in lipid solutions.
- alpha-Helix dipole model and electrostatic stabilization of 4-alpha-helical proteins.
- Free-energy determinants of alpha-helix insertion into lipid bilayers.
- Drosophila topoisomerase II double-strand DNA cleavage: analysis of DNA sequence homology at the cleavage site.