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Nucleic Acids Res. 2013 Sep;41(16):7815-27. doi: 10.1093/nar/gkt560. Epub 2013 Jun 26.

Structural insight into negative DNA supercoiling by DNA gyrase, a bacterial type 2A DNA topoisomerase.

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IGBMC, Integrated Structural Biology Department, UMR7104 CNRS, U964 Inserm, Université de Strasbourg, 67400 Illkirch, France, Institut de Chimie de Strasbourg, Université de Strasbourg, UMR7177 CNRS, 67000 Strasbourg, France and Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France.


Type 2A DNA topoisomerases (Topo2A) remodel DNA topology during replication, transcription and chromosome segregation. These multisubunit enzymes catalyze the transport of a double-stranded DNA through a transient break formed in another duplex. The bacterial DNA gyrase, a target for broad-spectrum antibiotics, is the sole Topo2A enzyme able to introduce negative supercoils. We reveal here for the first time the architecture of the full-length Thermus thermophilus DNA gyrase alone and in a cleavage complex with a 155 bp DNA duplex in the presence of the antibiotic ciprofloxacin, using cryo-electron microscopy. The structural organization of the subunits of the full-length DNA gyrase points to a central role of the ATPase domain acting like a 'crossover trap' that may help to sequester the DNA positive crossover before strand passage. Our structural data unveil how DNA is asymmetrically wrapped around the gyrase-specific C-terminal β-pinwheel domains and guided to introduce negative supercoils through cooperativity between the ATPase and β-pinwheel domains. The overall conformation of the drug-induced DNA binding-cleavage complex also suggests that ciprofloxacin traps a DNA pre-transport conformation.

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