title: A ParE-ParC fusion protein is a functional topoisomerase.
abstract: Type II topoisomerases are responsible for DNA unlinking during DNA replication and chromosome segregation. Although eukaryotic enzymes are homodimers and prokaryotic enzymes are heterotetramers, both prokaryotic and eukaryotic type II topoisomerases belong to a single protein family. The amino- and carboxyl-terminal domains of eukaryotic enzymes are homologous to the ATP-binding and catalytic subunits of prokaryotic enzymes, respectively. Topoisomerase IV, a prokaryotic type II topoisomerase, consists of the ATP-binding subunit, ParE, and the catalytic subunit, ParC. We have joined the coding regions of parE and parC in frame and constructed a fusion protein of the two subunits of topoisomerase IV. This fusion protein, ParEC, can catalyze both decatenation and relaxation reactions. The ParEC protein is also capable of decatenating replicating daughter DNA molecules during oriC DNA replication in vitro. Furthermore, the fusion gene, parEC, complements the temperature-sensitive growth of both parC and parE strains, indicating that the ParEC protein can substitute for topoisomerase IV in vivo. These results demonstrate that a fusion protein of the two subunits of topoisomerase IV is a functional topoisomerase. Thus, a heterotetrameric type II topoisomerase can be converted into a homodimeric type II topoisomerase by gene fusion.
authors.affiliation: Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
authors.forename: L S
authors.initials: LS
authors.lastname: Lavasani
authors.forename: H
authors.initials: H
authors.lastname: Hiasa
mesh_terms: D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D002384:Catalysis; D004261:DNA Replication; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II / Q000235:genetics* / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D005816:Genetic Complementation Test; D006868:Hydrolysis; D051738:Origin Recognition Complex; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000502:physiology*; D014764:Viral Proteins / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C114650:OriC chromosomal replication origin; D051738:Origin Recognition Complex; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; D027101:DNA Topoisomerase IV; D004250:DNA Topoisomerases, Type II