title: Action of site-specific recombinases XerC and XerD on tethered Holliday junctions.
abstract: In Xer site-specific recombination, two related recombinases, XerC and XerD, mediate the formation of recombinant products using Holliday junction-containing DNA molecules as reaction intermediates. Each recombinase catalyses the exchange of one pair of specific strands. By using synthetic Holliday junction-containing recombination substrates in which two of the four arms are tethered in an antiparallel configuration by a nine thymine oligonucleotide, we show that XerD catalyses efficient strand exchange only when its substrate strands are 'crossed'. XerC also catalyses very efficient strand exchange when its substrate strands are 'crossed', though it also appears to be able to mediate strand exchange when its substrate strands are 'continuous'. By using chemical probes of Holliday junction structure in the presence and absence of bound recombinases, we show that recombinase binding induces unstacking of the bases in the centre of the recombination site, indicating that the junction branch point is positioned there and is distorted as a consequence of recombinase binding.
authors.affiliation: Department of Biochemistry, University of Oxford, UK.
authors.forename: L K
authors.initials: LK
authors.lastname: Arciszewska
authors.forename: I
authors.initials: I
authors.lastname: Grainge
authors.forename: D J
authors.initials: DJ
authors.lastname: Sherratt
mesh_terms: D001426:Bacterial Proteins; D001665:Binding Sites; D002384:Catalysis; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D015245:Deoxyribonuclease BamHI / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins; D005296:Ferrous Compounds / Q000494:pharmacology; D017665:Hydroxyl Radical; D019426:Integrases; D009690:Nucleic Acid Conformation; D009993:Osmium Tetroxide / Q000494:pharmacology; D016877:Oxidants / Q000494:pharmacology; D011196:Potassium Permanganate / Q000494:pharmacology; D011506:Proteins; D045522:Recombinases; D013379:Substrate Specificity; D013941:Thymine
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D005296:Ferrous Compounds; D016877:Oxidants; D011506:Proteins; D045522:Recombinases; C473360:XerC protein, E coli; D011196:Potassium Permanganate; D017665:Hydroxyl Radical; C020748:ferrous sulfate; D004492:Edetic Acid; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C473361:XerD protein, E coli; C115006:integron integrase IntI1; D015245:Deoxyribonuclease BamHI; C024404:BglII endonuclease; D015252:Deoxyribonucleases, Type II Site-Specific; D009993:Osmium Tetroxide; D013941:Thymine