title: Xer-mediated site-specific recombination in vitro.
abstract: The Xer site-specific recombination system acts at ColE1 cer and pSC101 psi sites to ensure that these plasmids are in a monomeric state prior to cell division. We show that four proteins, ArgR, PepA, XerC and XerD are necessary and sufficient for recombination between directly repeated cer sites on a supercoiled plasmid in vitro. Only PepA, XerC and XerD are required for recombination at psi in vitro. Recombination at cer and psi in vitro requires negative supercoiling and is exclusively intramolecular. Strand exchange at cer produces Holliday junction-containing products in which only the top strands have been exchanged. This reaction requires the catalytic tyrosine residue of Xer C but not that of XerD. Recombination at psi gives catenated circular resolution products. Strand exchange at psi is sequential. XerC catalyses the first (top) strand exchange to make a Holiday junction intermediate and XerD catalyses the second (bottom) strand exchange.
authors.affiliation: Department of Biochemistry, University of Oxford, UK.
authors.forename: S D
authors.initials: SD
authors.lastname: Colloms
authors.forename: R
authors.initials: R
authors.lastname: McCulloch
authors.forename: K
authors.initials: K
authors.lastname: Grant
authors.forename: L
authors.initials: L
authors.lastname: Neilson
authors.forename: D J
authors.initials: DJ
authors.lastname: Sherratt
mesh_terms: D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004278:DNA, Superhelical / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins; D019426:Integrases; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D045522:Recombinases; D011995:Recombination, Genetic; D013379:Substrate Specificity
chemical_list: D004278:DNA, Superhelical; D029968:Escherichia coli Proteins; D045522:Recombinases; C473360:XerC protein, E coli; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C473361:XerD protein, E coli; C115006:integron integrase IntI1