title: Solution structures of DNA-bound gyrase.
abstract: The DNA gyrase negative supercoiling mechanism involves the assembly of a large gyrase/DNA complex and conformational rearrangements coupled to ATP hydrolysis. To establish the complex arrangement that directs the reaction towards negative supercoiling, bacterial gyrase complexes bound to 137- or 217-bp DNA fragments representing the starting conformational state of the catalytic cycle were characterized by sedimentation velocity and small-angle X-ray scattering (SAXS) experiments. The experiments revealed elongated complexes with hydrodynamic radii of 70-80 Å. Molecular envelopes calculated from these SAXS data show 2-fold symmetric molecules with the C-terminal domain (CTD) of the A subunit and the ATPase domain of the B subunit at opposite ends of the complexes. The proposed gyrase model, with the DNA binding along the sides of the molecule and wrapping around the CTDs located near the exit gate of the protein, adds new information on the mechanism of DNA negative supercoiling.
authors.affiliation: Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Baker
authors.forename: Steven
authors.initials: S
authors.lastname: Weigand
authors.forename: Sarah
authors.initials: S
authors.lastname: Maar-Mathias
authors.forename: Alfonso
authors.initials: A
authors.lastname: Mondragón
mesh_terms: D055162:Biocatalysis; D004247:DNA / Q000737:chemistry*; D027081:DNA Gyrase / Q000737:chemistry*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D004247:DNA; D027081:DNA Gyrase