title: Coordinated control of XerC and XerD catalytic activities during Holliday junction resolution.
abstract: Site-specific recombinases XerC and XerD function in the segregation of circular bacterial replicons. In a recombining nucleoprotein complex containing two molecules each of XerC and XerD, coordinated reciprocal switches in recombinase activity ensure that only XerC or XerD is active at any one time. Mutated recombinases that carry sub?stitutions of a catalytic arginine residue stimulate cleavage and strand exchange mediated by the partner recombinase on DNA substrates that are normally recombined poorly by the partner. This is associated with a reciprocal impairment of the recombinase's own ability to initiate catalysis. The extent of this switch in catalysis is modulated by changes in recombination site sequence and is not a direct consequence of any catalytic defect. We propose that altered interactions between the mutated proteins and their wild-type partners lead to an increased level of an alternative Holliday junction intermediate that has a conformation appropriate for resolution by the partner recombinase. The results indicate how subtle changes in protein-DNA architecture at a Holliday junction can redirect recombination outcome.
authors.affiliation: Division of Molecular Genetics Department of Biochemistry, University of Oxford, Oxford, OX1 3QU, UK.
authors.forename: L K
authors.initials: LK
authors.lastname: Arciszewska
authors.forename: R A
authors.initials: RA
authors.lastname: Baker
authors.forename: B
authors.initials: B
authors.lastname: Hallet
authors.forename: D J
authors.initials: DJ
authors.lastname: Sherratt
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites; D002384:Catalysis; D004254:DNA Nucleotidyltransferases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics*; D029968:Escherichia coli Proteins; D019426:Integrases; D007700:Kinetics; D009154:Mutation / Q000235:genetics; D009690:Nucleic Acid Conformation; D010641:Phenotype; D011485:Protein Binding; D045522:Recombinases; D011995:Recombination, Genetic / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D013379:Substrate Specificity
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D045522:Recombinases; C473360:XerC protein, E coli; D001120:Arginine; D004254:DNA Nucleotidyltransferases; D019426:Integrases; C473361:XerD protein, E coli; C115006:integron integrase IntI1