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

作者：Nolivos Sophie; Pages Carine; Rousseau Philippe; Le Bourgeois Pascal; Cornet Francois^*

来源：Nucleic Acids Research, 2010, 38(19): 6477-6489.

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/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 FtsK gamma subdomain. However, FtsK gamma activates recombination through different mechanisms in these two Xer systems. We show that FtsK gamma alone activates XerCD/dif recombination. In contrast, both FtsK gamma and the translocation motor are required to activate XerS/dif(SL) recombination. These findings have implications for the mechanisms by which FtsK activates recombination.

• 出版日期2010-10