Asymmetric DNA requirements in Xer recombination activation by FtsK.

Publication Type:

Journal Article

Source:

Nucleic acids research, Volume 37, Issue 7, p.2371-80 (2009)

DOI:

10.1093/nar/gkp104

Keywords:

Base Sequence; DNA Helicases; DNA, Bacterial; Escherichia coli; Escherichia coli Proteins; Integrases; Membrane Proteins; Nucleotides; Recombination, Genetic

Abstract:

In bacteria with circular chromosomes, homologous recombination events can lead to the formation of chromosome dimers. In Escherichia coli, chromosome dimers are resolved by the addition of a crossover by two tyrosine recombinases, XerC and XerD, at a specific site on the chromosome, dif. Recombination depends on a direct contact between XerD and a cell division protein, FtsK, which functions as a hexameric double stranded DNA translocase. Here, we have investigated how the structure and composition of DNA interferes with Xer recombination activation by FtsK. XerC and XerD each cleave a specific strand on dif, the top and bottom strand, respectively. We found that the integrity and nature of eight bottom-strand nucleotides and three top-strand nucleotides immediately adjacent to the XerD-binding site of dif are crucial for recombination. These nucleotides are probably not implicated in FtsK translocation since FtsK could translocate on single stranded DNA in both the 5'-3' and 3'-5' orientation along a few nucleotides. We propose that they are required to stabilize FtsK in the vicinity of dif for recombination to occur because the FtsK-XerD interaction is too transient or too weak in itself to allow for XerD catalysis.

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