大肠杆菌细胞分裂中 FtsEX 系统水解肽聚糖的结构机制
Structural insights into peptidoglycan hydrolysis by the FtsEX system in Escherichia coli during cell division
研究解析了大肠杆菌（Escherichia coli）FtsEX 复合物在细胞分裂中调控肽聚糖水解的结构机制，发现 ATP 对复合物稳定起关键作用，且该作用跨物种保守。EnvC 结合后 FtsEX 的 ATPase 活性显著升高；有、无 EnvC 时的高分辨率结构显示 Eco FtsEX 呈对称构象，可通过周质结构域中的柔性环容纳 EnvC 的固有不对称性。负染成像显示 Eco FtsEX/EnvC/AmiB 形成类似铜绿假单胞菌（Pseudomonas aeruginosa）FtsEX 系统的细长复合物。
来源：eLife · doi.org
Bacterial cell division relies on precise peptidoglycan (PG) remodeling, a process orchestrated by the FtsEX complex. Comprised of FtsE and FtsX, this complex collaborates with EnvC, a periplasmic lytic enzyme activator, to regulate septal PG hydrolysis by amidases like AmiB. While recent structural investigations, particularly of Pseudomonas aeruginosa FtsEX ( Pae FtsEX), have shed light on complex interactions and proposed activation mechanisms, the structural intricacies governing PG degradation by the FtsEX complex and EnvC in Escherichia coli cytokinesis remain unexplored. In this study, we present a comprehensive biochemical and structural analysis of E. coli FtsEX complexes, unveiling a key role for ATP in complex stabilization that extends across bacterial species. Upon EnvC binding, ATPase activity markedly increases. High-resolution structures of Eco FtsEX, both in the presence and absence of EnvC, reveal a symmetrical conformation of Eco FtsEX capable of accommodating the inherent asymmetry of EnvC, mediated by flexible loops within the periplasmic domain. Our negative-staining imaging showcases an elongated Eco FtsEX/EnvC/AmiB complex reminiscent of the Pae FtsEX system. These findings collectively provide intricate insights into the regulation of PG cleavage by FtsEX in E. coli —a pivotal model system used in pilot genetic studies, suggesting a conserved mechanism for precise hydrolase activation in bacteria.