title: Small-angle X-ray scattering reveals the solution structure of the full-length DNA gyrase a subunit.
abstract: DNA gyrase is the topoisomerase uniquely able to actively introduce negative supercoils into DNA. Vital in all bacteria, but absent in humans, this enzyme is a successful target for antibacterial drugs. From biophysical experiments in solution, we report the low-resolution structure of the full-length A subunit (GyrA). Analytical ultracentrifugation shows that GyrA is dimeric, but nonglobular. Ab initio modeling from small-angle X-ray scattering allows us to retrieve the molecular envelope of GyrA and thereby the organization of its domains. The available crystallographic structure of the amino-terminal domain (GyrA59) forms a dimeric core, and two additional pear-shaped densities closely flank it in an unexpected position. Each accommodates very well a carboxyl-terminal domain (GyrA-CTD) built from a homologous crystallographic structure. The uniqueness of gyrase is due to the ability of the GyrA-CTDs to wrap DNA. Their position within the GyrA structure strongly suggests a large conformation change of the enzyme upon DNA binding.
authors.affiliation: Department of Biological Chemistry, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, United Kingdom.
authors.forename: Lionel
authors.initials: L
authors.lastname: Costenaro
authors.forename: J Günter
authors.initials: JG
authors.lastname: Grossmann
authors.forename: Christine
authors.initials: C
authors.lastname: Ebel
authors.forename: Anthony
authors.initials: A
authors.lastname: Maxwell
mesh_terms: D000595:Amino Acid Sequence; D027081:DNA Gyrase / Q000737:chemistry*; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology*; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D012996:Solutions / Q000737:chemistry; D014461:Ultracentrifugation; D014961:X-Ray Diffraction
chemical_list: D012996:Solutions; D027081:DNA Gyrase