Are two better than one? Analysis of an FtsK/Xer recombination system that uses a single recombinase

• Published in: Nucleic acids research Vol. 38; no. 19; pp. 6477 - 6489
• Main Authors: Nolivos, Sophie, Pages, Carine, Rousseau, Philippe, Le Bourgeois, Pascal, Cornet, François
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 01.10.2010
• Subjects: Amino Acid Sequence; Binding Sites; Cell division; Chromosome translocations; Chromosomes; Chromosomes, Bacterial - metabolism; Dimerization; DNA; Escherichia coli; Escherichia coli - enzymology; Escherichia coli - genetics; Escherichia coli Proteins - metabolism; Genome Integrity, Repair and; Lactococcus lactis; Lactococcus lactis - enzymology; Lactococcus lactis - genetics; Membrane Proteins - metabolism; Molecular Sequence Data; Proteobacteria; recombinase; Recombinases - metabolism; Recombination; Recombination, Genetic; translocase
• ISSN: 0305-1048; 1362-4962; 1362-4962
• DOI: 10.1093/nar/gkq507

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/difSL system, include only one recombinase. We investigated the functional effects of this difference by studying the XerS/difSL system. XerS bound and recombined difSL sites in vitro, both activities displaying asymmetric characteristics. Resolution of chromosome dimers by XerS/difSL 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/difSL. 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/difSL 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/difSL recombination. These findings have implications for the mechanisms by which FtsK activates recombination.