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Quinolone mode of action--new aspects
1Infectious Disease Unit, Massachusetts General Hospital, Harvard Medical School, Boston.
Drugs
|January 1, 1993
Summary
Quinolone antibiotics interact with DNA gyrase and DNA complexes. Specific amino acid changes in GyrA and GyrB subunits alter bacterial susceptibility to these drugs.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Quinolones are a class of antibiotics that target bacterial DNA gyrase.
- Understanding quinolone-DNA gyrase interactions is crucial for developing new antibacterial agents.
Purpose of the Study:
- To elucidate the molecular interactions between quinolones and the DNA gyrase-DNA complex.
- To identify specific amino acid residues in DNA gyrase subunits responsible for quinolone susceptibility.
Main Methods:
- Sequencing of mutant gyrA and gyrB genes from Escherichia coli.
- Analysis of amino acid substitutions and their correlation with quinolone susceptibility.
- Binding studies of norfloxacin and ciprofloxacin to DNA gyrase-DNA complexes.
Main Results:
- Specific amino acid positions in GyrA (67-106) and GyrB (426, 447) are critical for quinolone action.
- Mutations at GyrB positions 426 and 447 suggest direct electrostatic interactions with quinolones.
- Serine at position 83 in GyrA is important for enzyme and bacterial susceptibility.
- Norfloxacin and ciprofloxacin bind most effectively to the gyrase-DNA complex.
Conclusions:
- Bacterial resistance to quinolones is linked to specific mutations in DNA gyrase subunits.
- Quinolone binding is dependent on the integrity of the gyrase-DNA complex.
- Topoisomerase IV, homologous to DNA gyrase, is also inhibited by some quinolones.