Institute for Science and Technology Austria (IST Austria), Klosterneuburg, Austria.
University of Vienna, Department of Pharmaceutical Sciences, Vienna, Austria.
Nat Commun. 2022 May 12;13(1):2635. doi: 10.1038/s41467-022-30301-y.
The actin-homologue FtsA is essential for E. coli cell division, as it links FtsZ filaments in the Z-ring to transmembrane proteins. FtsA is thought to initiate cell constriction by switching from an inactive polymeric to an active monomeric conformation, which recruits downstream proteins and stabilizes the Z-ring. However, direct biochemical evidence for this mechanism is missing. Here, we use reconstitution experiments and quantitative fluorescence microscopy to study divisome activation in vitro. By comparing wild-type FtsA with FtsA R286W, we find that this hyperactive mutant outperforms FtsA WT in replicating FtsZ treadmilling dynamics, FtsZ filament stabilization and recruitment of FtsN. We could attribute these differences to a faster exchange and denser packing of FtsA R286W below FtsZ filaments. Using FRET microscopy, we also find that FtsN binding promotes FtsA self-interaction. We propose that in the active divisome FtsA and FtsN exist as a dynamic copolymer that follows treadmilling filaments of FtsZ.
肌动蛋白同源物 FtsA 对大肠杆菌细胞分裂至关重要，因为它将 Z 环中的 FtsZ 丝与跨膜蛋白连接起来。人们认为 FtsA 通过从无活性的聚合态切换到有活性的单体构象来启动细胞缢缩，这种构象募集下游蛋白并稳定 Z 环。然而，这种机制的直接生化证据尚缺乏。在这里，我们使用重组实验和定量荧光显微镜在体外研究分裂体的激活。通过比较野生型 FtsA 和 FtsA R286W，我们发现这种超活性突变体在复制 FtsZ treadmilling 动力学、稳定 FtsZ 丝和募集 FtsN 方面优于 FtsA WT。我们可以将这些差异归因于 FtsA R286W 与 FtsZ 丝下 FtsA WT 的更快交换和更密集的包装。使用 FRET 显微镜，我们还发现 FtsN 结合促进 FtsA 自身相互作用。我们提出，在活跃的分裂体中，FtsA 和 FtsN 作为一种动态共聚物存在，该共聚物沿着 FtsZ 的 treadmilling 丝移动。
