3.A.1.140.1
The FtsX/FtsE ABC transporter (Arends et al., 2009) (FtsX is of the type III topology). FtsEX directly recruits EnvC to the septum via an interaction between EnvC and a periplasmic loop of FtsX. FtsEX variants predicted to be ATPase defective still recruit EnvC to the septum but fail to promote cell separation. Amidase activation via EnvC in the periplasm is regulated by conformational changes in the FtsEX complex mediated by ATP hydrolysis in the cytoplasm. Since FtsE has been reported to interact with FtsZ, amidase activity may be coupled with the contraction of the FtsZ cytoskeletal ring (Yang et al., 2011).  The hydrolysis of septal PG (sPG) is a crucial step of bacterial cell division, facilitated by FtsEX through an amidase activation system. Chen et al. 2024 presented the cryo-EM structures of Escherichia coli FtsEX and FtsEX-EnvC in the ATP-bound state at resolutions of 3.05 Å and 3.11 Å, respectively. The PG degradation assays in E. coli revealed that the ATP-bound conformation of FtsEX activates sPG hydrolysis of EnvC-AmiB, whereas EnvC-AmiB alone exhibits autoinhibition. Structural analyses indicate that ATP binding induces conformational changes in FtsEX-EnvC. PG degradation assays of AmiB mutants confirm that the regulation of AmiB by FtsEX-EnvC is achieved through the interaction between EnvC-AmiB. These findings provide structural insight into the mechanism of sPG hydrolysis and bacterial cell division (Chen et al. 2024).