title: Are two better than one? Analysis of an FtsK/Xer recombination system that uses a single recombinase.
abstract: Bacteria harbouring circular chromosomes have a Xer site-specific recombination system that resolves chromosome dimers at division. In Escherichia coli, the activity of the XerCD/dif system is controlled and coupled with cell division by the FtsK DNA translocase. Most Xer systems, as XerCD/dif, include two different recombinases. However, some, as the Lactococcus lactis XerS/dif(SL) system, include only one recombinase. We investigated the functional effects of this difference by studying the XerS/dif(SL) system. XerS bound and recombined dif(SL) sites in vitro, both activities displaying asymmetric characteristics. Resolution of chromosome dimers by XerS/dif(SL) required translocation by division septum-borne FtsK. The translocase domain of L. lactis FtsK supported recombination by XerCD/dif, just as E. coli FtsK supports recombination by XerS/dif(SL). Thus, the FtsK-dependent coupling of chromosome segregation with cell division extends to non-rod-shaped bacteria and outside the phylum Proteobacteria. Both the XerCD/dif and XerS/dif(SL) recombination systems require the control activities of the FtsKγ subdomain. However, FtsKγ activates recombination through different mechanisms in these two Xer systems. We show that FtsKγ alone activates XerCD/dif recombination. In contrast, both FtsKγ and the translocation motor are required to activate XerS/dif(SL) recombination. These findings have implications for the mechanisms by which FtsK activates recombination.
authors.affiliation: Laboratoire de Microbiologie et de Génétique Moléculaire, CNRS and Université de Toulouse, Université Paul Sabatier, F-31000 Toulouse, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Nolivos
authors.forename: Carine
authors.initials: C
authors.lastname: Pages
authors.forename: Philippe
authors.initials: P
authors.lastname: Rousseau
authors.forename: Pascal
authors.initials: P
authors.lastname: Le Bourgeois
authors.forename: François
authors.initials: F
authors.lastname: Cornet
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002876:Chromosomes, Bacterial / Q000378:metabolism; D019281:Dimerization; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000378:metabolism; D013294:Lactococcus lactis / Q000201:enzymology / Q000235:genetics*; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D045522:Recombinases / Q000378:metabolism*; D011995:Recombination, Genetic
chemical_list: D029968:Escherichia coli Proteins; C096452:FtsK protein, E coli; D008565:Membrane Proteins; D045522:Recombinases