Blackwell Publishing Journal Backfiles 1879-2005
Escherichia coli FtsK is a multifunctional protein that couples cell division and chromosome segregation. Its N-terminal transmembrane domain (FtsKN) is essential for septum formation, whereas its C-terminal domain (FtsKC) is required for chromosome dimer resolution by XerCD-dif site-specific recombination. FtsKC is an ATP-dependent DNA translocase. In vitro and in vivo data point to a dual role for this domain in chromosome dimer resolution (i) to directly activate recombination by XerCD-dif and (ii) to bring recombination sites together and/or to clear DNA from the closing septum. FtsKN and FtsKC are separated by a long linker region (FtsKL) of unknown function that is highly divergent between bacterial species. Here, we analysed the in vivo effects of deletions of FtsKL and/or of FtsKC, of swaps of these domains with their Haemophilus influenzae counterparts and of a point mutation that inactivates the walker A motif of FtsKC. Phenotypic characterization of the mutants indicated a role for FtsKL in cell division. More importantly, even though Xer recombination activation and DNA mobilization both rely on the ATPase activity of FtsKC, mutants were found that can perform only one or the other of these two functions, which allowed their separation in vivo for the first time.
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