Structural insights into peptidoglycan hydrolysis by the FtsEX system inEscherichia coliduring 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 ofPseudomonas aeruginosaFtsEX (PaeFtsEX), have shed light on complex interactions and proposed activation mechanisms, the structural intricacies governing PG degradation by the FtsEX complex and EnvC inEscherichia colicytokinesis remain unexplored. In this study, we present a comprehensive biochemical and structural analysis ofE. coliFtsEX 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 ofEcoFtsEX, both in the presence and absence of EnvC, reveal a symmetrical conformation ofEcoFtsEX capable of accommodating the inherent asymmetry of EnvC, mediated by flexible loops within the periplasmic domain. Our negative-staining imaging showcases an elongatedEcoFtsEX/EnvC/AmiB complex reminiscent of thePaeFtsEX system. These findings collectively provide intricate insights into the regulation of PG cleavage by FtsEX inE. coli- a pivotal model system used in pilot genetic studies, suggesting a conserved mechanism for precise hydrolase activation in bacteria.