Structural insights into peptidoglycan hydrolysis by the FtsEX system in Escherichia coli during cell division

Bacterial cell division relies on precise peptidoglycan (PG) remodelling, 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 (PaeFtsEX), 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 EcoFtsEX, both in the presence and absence of EnvC, reveal a symmetrical conformation of EcoFtsEX capable of accommodating the inherent asymmetry of EnvC, mediated by flexible loops within the periplasmic domain. Our negative-staining imaging showcases an elongated EcoFtsEX/EnvC/AmiB complex reminiscent of the PaeFtsEX 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.