Lyu Zhixin, Yang Xinxing, Yahashiri Atsushi, Ha Stephen, McCausland Joshua W, Chen Xinlei, Britton Brooke M, Weiss David S, Xiao Jie
Department of Biophysics and Biophysical Chemistry, Johns Hopkins School of Medicine, Baltimore, MD, USA.
Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.
Nat Microbiol. 2025 May 27. doi: 10.1038/s41564-025-02011-w.
In Escherichia coli, FtsN is thought to coordinate septal peptidoglycan (sPG) synthesis and degradation. Its E domain interacts with the sPG synthesis complex, FtsWIQLB, and its SPOR domain interacts with denuded glycan (dnG), intermediates of sPG degradation. Here we used single-molecule tracking of FtsN and FtsW to investigate how FtsN coordinates the two opposing processes. We found that the SPOR domain binds to dnG cooperatively. This binding sequesters FtsWIQLB on dnG, which we call the dnG-track, and prevents dnG degradation. SPOR domain's release from dnGs exposes dnGs to degradation, moves FtsN to the sPG synthesis track and activates FtsWIQLB. In addition, FtsN self-interacts through the SPOR domain, promoting the multimerization of FtsWIQLB on both tracks. This self-interaction may create a sensitive switch, regulating FtsN's partitioning between dnG- and sPG-tracks to coordinate sPG degradation and synthesis while also controlling the balance between sequestered and active populations of the sPG synthesis complex. Our data reveal a third track that plays an important role in sPG synthesis and degradation across space and time, complementing the previously discovered sPG-track and FtsZ-track in E. coli for robust septal cell wall constriction.
在大肠杆菌中，FtsN被认为可协调隔膜肽聚糖（sPG）的合成与降解。其E结构域与sPG合成复合物FtsWIQLB相互作用，其SPOR结构域与裸露聚糖（dnG，即sPG降解的中间体）相互作用。在此，我们利用FtsN和FtsW的单分子追踪技术来研究FtsN如何协调这两个相反的过程。我们发现SPOR结构域与dnG协同结合。这种结合将FtsWIQLB隔离在dnG上，我们将其称为dnG轨道，并阻止dnG降解。SPOR结构域从dnG上释放会使dnG暴露于降解，将FtsN转移到sPG合成轨道并激活FtsWIQLB。此外，FtsN通过SPOR结构域进行自身相互作用，促进FtsWIQLB在两条轨道上的多聚化。这种自身相互作用可能会产生一个敏感开关，调节FtsN在dnG轨道和sPG轨道之间的分配，以协调sPG的降解与合成，同时还控制sPG合成复合物的隔离群体与活性群体之间的平衡。我们的数据揭示了第三条轨道，它在sPG跨时空的合成与降解中发挥重要作用，补充了大肠杆菌中先前发现的sPG轨道和FtsZ轨道，以实现强大的隔膜细胞壁收缩。
