In many bacteria, cell division begins before the sister chromosomes are fully segregated. Specific DNA translocases ensure that the chromosome is removed from the closing septum, such as the transmembrane protein FtsK in Escherichia coli. Bacillus subtilis contains two FtsK homologues, SpoIIIE and SftA. SftA is active during vegetative growth whereas SpoIIIE is primarily active during sporulation and pumps the chromosome into the spore compartment. FtsK and SpoIIIE contain several transmembrane helices, however, SftA is assumed to be a cytoplasmic protein. It is unknown how SftA is recruited to the cell division site. Here we show that SftA is a peripheral membrane protein, containing an N-terminal amphipathic helix that reversibly anchors the protein to the cell membrane. Using a yeast two-hybrid screen we found that SftA interacts with the conserved cell division protein SepF. Based on extensive genetic analyses and previous data we propose that the septal localization of SftA depends on either SepF or the cell division protein FtsA. Since SftA seems to interfere with the activity of SepF, and since inactivation of SepF mitigates the sensitivity of a ∆sftA mutant for ciprofloxacin, we speculate that SftA might delay septum synthesis when chromosomal DNA is in the vicinity.

中文翻译：

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SepF 支持将 DNA 转位酶 SftA 募集到 Z 环

在许多细菌中，细胞分裂在姐妹染色体完全分离之前就开始了。特定的 DNA 转位酶确保染色体从关闭的隔膜中移除，例如大肠杆菌中的跨膜蛋白 FtsK 。枯草芽孢杆菌包含两个 FtsK 同系物，SpoIIIE 和 SftA。SftA 在营养生长过程中是活跃的，而 SpoIIIE 在孢子形成过程中主要是活跃的，并将染色体泵入孢子室。FtsK 和 SpoIIIE 包含几个跨膜螺旋，然而，SftA 被认为是一种细胞质蛋白。尚不清楚 SftA 是如何被招募到细胞分裂部位的。在这里，我们表明 SftA 是一种外周膜蛋白，包含一个 N 端两亲螺旋，可将蛋白质可逆地锚定到细胞膜上。使用酵母双杂交筛选，我们发现 SftA 与保守的细胞分裂蛋白 SepF 相互作用。基于广泛的遗传分析和先前的数据，我们提出 SftA 的隔膜定位取决于 SepF 或细胞分裂蛋白 FtsA。由于 SftA 似乎干扰了 SepF 的活动，环丙沙星的sftA突变体，我们推测当染色体 DNA 在附近时，SftA 可能会延迟隔膜合成。