DNA gyrase subunit alpha (GyrA)

DNA gyrase subunit alpha (GyrA) is one of the two essential catalytic subunits (A and B) that constitute bacterial DNA gyrase, a unique type II topoisomerase enzyme that introduces negative supercoils into closed circular double-stranded DNA in an ATP-dependent manner[2][4][5][6][8][10][14]. GyrA harbors the active-site tyrosine that covalently attaches to DNA during the cleavage step, and its C-terminal domain (CTD) bends and wraps DNA, enabling strand passage and supercoil introduction[9][13]. Together with the GyrB subunit, it forms a heterotetrameric complex (A2B2), essential for genome replication and transcription by managing DNA topology, removing positive supercoils ahead of advancing polymerases, and decatenating replicated chromosomes[4][5].\nGyrA is widely conserved among bacteria; it is the direct target of numerous antibiotics (e.g., fluoroquinolones, gepotidacin, novobiocin), and mutations in gyrA confer clinically significant resistance to such agents. Its critical, nonredundant function in prokaryotic organisms and lack of close eukaryotic homologs (outside plastid enzymes) make GyrA a cornerstone target for antibacterial drug development[4][7][10].

Other names

DNA gyrase subunit AGyrADNA gyrase ADNA topoisomerase II subunit A

Inhibition of DNA supercoiling by preventing strand re-ligation (fluoroquinolones trap the enzyme-DNA complex); Inhibition of ATPase activity (novobiocin); Interference with DNA cleavage or strand passage