The essential domain of FtsN triggers cell division by promoting interaction between FtsL and FtsI

Abstract

Cell division in bacteria requires the activation of FtsWI at the division site to synthesize septal peptidoglycan. In E. coli FtsN activates FtsWI and a previous model posited that the essential domain of FtsN (EFtsN) acts on FtsQLB causing conformational changes so that a domain of FtsL, called AWI (AWIFtsL), contacts FtsI resulting in activation of FtsW. In this study we use genetic analysis along with an AlphaFold2 model to test this activation model. Based on our findings we propose an updated model wherein the AWIFtsL and FtsI interaction is stabilized by EFtsN to activate FtsW and that this interaction is enhanced by the CytoFtsN-FtsA interaction. Thus, FtsN acts as both a sensor for divisome assembly and an activator. In addition, we elucidate the role played by two critical FtsL residues in FtsW activation.