CNRS, Centre de Génétique Moléculaire, Gif-sur-Yvette, France.
EMBO J. 2010 Feb 3;29(3):597-605. doi: 10.1038/emboj.2009.381. Epub 2009 Dec 24.
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.
在细菌中，隔膜的形成通常先于染色体分离的最后步骤。当染色体二聚体通过同源重组形成时，情况尤其如此。染色体分离然后需要一种双链 DNA 转运蛋白的活性，该转运蛋白通过一个整合的膜结构域（FtsK）锚定在隔膜上。有人提出，FtsK 家族蛋白的跨膜片段在脂质双层中形成孔，用于 DNA 的运输。在这里，我们表明，如果截短的大肠杆菌 FtsK 蛋白缺失所有的 FtsK 跨膜片段，并且通过足够长的接头与隔膜靶向肽连接，它们可以有效地解决染色体二聚体的问题。这些结果表明，FtsK 不需要通过其整合的膜结构域形成的孔来运输 DNA。因此，我们提出 FtsK 在膜融合之前运输 DNA，此时在收缩的隔膜中仍然有一个开口。
