DNA Gyrase - Inhibition By Antibiotics

Inhibition By Antibiotics

Gyrase is present in prokaryotes and some eukaryotes, but the enzymes are not entirely similar in structure or sequence, and have different affinities for different molecules. It is not present in humans. This makes gyrase a good target for antibiotics. Two classes of antibiotics that inhibit gyrase are:

• The aminocoumarins (including novobiocin). Aminocoumarins work by competitive inhibition of energy transduction of DNA gyrase by binding to the ATPase active site located on the GyrB subunit.
• The quinolones (including nalidixic acid and ciprofloxacin). Quinolones bind these enzymes and prevent them from decatenating replicating DNA. Quinolone-resistant bacteria frequently harbor mutated topoisomerases that resist quinolone binding.

DNA gyrase has two subunits,which in turn have two subunits each, i.e. 2A and 2B SUBUNITS.The A subunit carries out nicking of DNA,B subunit introduces negative supercoils,and then A subunit reseals the strands.Fluorquinolones bind to the A subunit and interfere with its strand cutting and resealing function.