title: Modular structure of the full-length DNA gyrase B subunit revealed by small-angle X-ray scattering.
abstract: DNA gyrase, the only topoisomerase able to introduce negative supercoils into DNA, is essential for bacterial transcription and replication; absent from humans, it is a successful target for antibacterials. From biophysical experiments in solution, we report a structural model at approximately 12-15 A resolution of the full-length B subunit (GyrB). Analytical ultracentrifugation shows that GyrB is mainly a nonglobular monomer. Ab initio modeling of small-angle X-ray scattering data for GyrB consistently yields a "tadpole"-like envelope. It allows us to propose an organization of GyrB into three domains-ATPase, Toprim, and Tail-based on their crystallographic and modeled structures. Our study reveals the modular organization of GyrB and points out its potential flexibility, needed during the gyrase catalytic cycle. It provides important insights into the supercoiling mechanism by gyrase and suggests new lines of research.
authors.affiliation: Department of Biological Chemistry, John Innes Centre, 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*; D004926:Escherichia coli / Q000201:enzymology; D008969:Molecular Sequence Data; D021122:Protein Subunits / Q000737:chemistry*; D053838:Scattering, Small Angle; D012996:Solutions; D014961:X-Ray Diffraction
chemical_list: D021122:Protein Subunits; D012996:Solutions; D027081:DNA Gyrase