Protection of the chromosome from scission by the division machinery during cytokinesis is critical for bacterial survival and fitness. This is achieved by nucleoid occlusion, which, in conjunction with other mechanisms, ensures formation of the division ring at midcell. In Escherichia coli, this mechanism is mediated by SlmA, a specific DNA binding protein that antagonizes assembly of the central division protein FtsZ into a productive ring in the vicinity of the chromosome. Here, we provide evidence supporting direct interaction of SlmA with lipid membranes, tuned by its binding partners FtsZ and SlmA binding sites (SBS) on chromosomal DNA. Reconstructions in minimal membrane systems that mimic cellular environments show that SlmA binds to lipid-coated microbeads or locates at the edge of microfluidic-generated microdroplets, inside which the protein is encapsulated. DNA fragments containing SBS sequences do not seem to be recruited to the membrane by SlmA but instead compete with SlmA’s ability to bind lipids. The interaction of SlmA with FtsZ modulates this behavior, ultimately triggering membrane localization of the SBS sequences alongside the two proteins. The ability of SlmA to bind lipids uncovered in this work extends the interaction network of this multivalent regulator beyond its well-known protein and nucleic acid recognition, which may have implications in the overall spatiotemporal control of division ring assembly.

中文翻译：

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核样闭塞蛋白S1mA结合到脂质膜上。

在胞质分裂过程中保护染色体免受分裂机制的分裂对于细菌存活和适应性至关重要。这是通过核苷闭塞实现的，与其他机制结合，可确保在中细胞形成分裂环。在大肠杆菌中，这种机制是由SlmA介导的，SlmA是一种特殊的DNA结合蛋白，可拮抗中央分裂蛋白FtsZ组装成染色体附近的生产环。在这里，我们提供了支持SlmA与脂质膜直接相互作用的证据，并通过其结合伴侣FtsZ和SlmA结合位点（SBS）调节了染色体DNA。在模仿细胞环境的最小膜系统中的重建显示，SlmA结合到脂质包裹的微珠上或位于微流产生的微滴的边缘，蛋白质被包裹在其中。含有SBS序列的DNA片段似乎不会被S1mA募集到膜上，而是与S1mA结合脂质的能力竞争。SlmA与FtsZ的相互作用调节了这种行为，最终触发了SBS序列与这两种蛋白一起的膜定位。S1mA结合在这项工作中发现的脂质的能力将这种多价调节剂的相互作用网络扩展到其众所周知的蛋白质和核酸识别之外，这可能对分割环组装的总体时空控制有影响。