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Fully efficient chromosome dimer resolution in Escherichia coli cells lacking the integral membrane domain of FtsK.

ABSTRACT: In bacteria, septum formation frequently initiates before the last steps of chromosome segregation. This is notably the case when chromosome dimers are formed by homologous recombination. Chromosome segregation then requires the activity of a double-stranded DNA transporter anchored at the septum by an integral membrane domain, FtsK. It was proposed that the transmembrane segments of proteins of the FtsK family form pores across lipid bilayers for the transport of DNA. Here, we show that truncated Escherichia coli FtsK proteins lacking all of the FtsK transmembrane segments allow for the efficient resolution of chromosome dimers if they are connected to a septal targeting peptide through a sufficiently long linker. These results indicate that FtsK does not need to transport DNA through a pore formed by its integral membrane domain. We propose therefore that FtsK transports DNA before membrane fusion, at a time when there is still an opening in the constricted septum.

SUBMITTER: Dubarry N

PROVIDER: S-EPMC2830691 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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Fully efficient chromosome dimer resolution in Escherichia coli cells lacking the integral membrane domain of FtsK.

Dubarry Nelly N Barre François-Xavier FX

The EMBO journal 20091224 3

In bacteria, septum formation frequently initiates before the last steps of chromosome segregation. This is notably the case when chromosome dimers are formed by homologous recombination. Chromosome segregation then requires the activity of a double-stranded DNA transporter anchored at the septum by an integral membrane domain, FtsK. It was proposed that the transmembrane segments of proteins of the FtsK family form pores across lipid bilayers for the transport of DNA. Here, we show that truncat ...[more]

PMID: 20033058

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Project description:Chromosome dimers occur in bacterial cells as a result of the recombinational repair of DNA. In most bacteria, chromosome dimers are resolved by XerCD site-specific recombination at the dif (deletion-induced filamentation) site located in the terminus region of the chromosome. Caulobacter crescentus, a Gram-negative oligotrophic bacterium, also possesses Xer recombinases, called CcXerC and CcXerD, which have been shown to interact with the Escherichia colidif site in vitro Previous studies on Caulobacter have suggested the presence of a dif site (referred to in this paper as dif1CC ), but no in vitro data have shown any association with this site and the CcXer proteins. Using recursive hidden Markov modeling, another group has proposed a second dif site, which we call dif2CC , which shows more similarity to the dif consensus sequence. Here, by using a combination of in vitro experiments, we compare the affinities and the cleavage abilities of CcXerCD recombinases for both dif sites. Our results show that dif2CC displays a higher affinity for CcXerC and CcXerD and is bound cooperatively by these proteins, which is not the case for the original dif1CC site. Furthermore, dif2CC nicked substrates are more efficiently cleaved by CcXerCD, and deletion of the site results in about 5 to 10% of cells showing an altered cellular morphology.IMPORTANCE Bacteria utilize site-specific recombination for a variety of purposes, including the control of gene expression, acquisition of genetic elements, and the resolution of dimeric chromosomes. Failure to resolve dimeric chromosomes can lead to cell division defects in a percentage of the cell population. The work presented here shows the existence of a chromosomal resolution system in C. crescentus Defects in this resolution system result in the formation of chains of cells. Further understanding of how these cells remain linked together will help in the understanding of how chromosome segregation and cell division are linked in C. crescentus.

Dataset Information

Fully efficient chromosome dimer resolution in Escherichia coli cells lacking the integral membrane domain of FtsK.

Publications

Fully efficient chromosome dimer resolution in Escherichia coli cells lacking the integral membrane domain of FtsK.

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