title: Reverse gyrase transiently unwinds double-stranded DNA in an ATP-dependent reaction.
abstract: Reverse gyrase is a unique DNA topoisomerase that catalyzes the introduction of positive supercoils into DNA in an ATP-dependent reaction. It consists of a helicase domain that functionally cooperates with a topoisomerase domain. Different models for the catalytic mechanism of reverse gyrase that predict a central role of the helicase domain have been put forward. The helicase domain acts as a nucleotide-dependent conformational switch that alternates between open and closed states with different affinities for single- and double-stranded DNA. It has been suggested that the helicase domain can unwind double-stranded regions, but helicase activity has not been demonstrated as yet. Here, we show that the isolated helicase domain and full-length reverse gyrase can transiently unwind double-stranded regions in an ATP-dependent reaction. The latch region of reverse gyrase, an insertion into the helicase domain, is required for DNA supercoiling. Strikingly, the helicase domain lacking the latch cannot unwind DNA, linking unwinding to DNA supercoiling. The unwinding activity may provide and stabilize the single-stranded regions required for strand passage by the topoisomerase domain, either de novo or by expanding already existing unpaired regions that may form at high temperatures.
authors.affiliation: Institute for Physical Chemistry, University of Muenster, Corrensstrasse 30, D-48149 Muenster, Germany.
authors.forename: Agneyo
authors.initials: A
authors.lastname: Ganguly
authors.forename: Yoandris
authors.initials: Y
authors.lastname: del Toro Duany
authors.forename: Dagmar
authors.initials: D
authors.lastname: Klostermeier
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000235:genetics*; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D004278:DNA, Superhelical / Q000235:genetics*; D008958:Models, Molecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D020124:Thermotoga maritima / Q000201:enzymology* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D000255:Adenosine Triphosphate; D004247:DNA; D004265:DNA Helicases; C041813:DNA reverse gyrase; D004264:DNA Topoisomerases, Type I