Structure of the heterotrimeric membrane protein complex FtsB-FtsL-FtsQ of the bacterial divisome

The synthesis of the cell-wall peptidoglycan during bacterial cell division is mediated by a multiprotein machine, called the divisome. The essential membrane protein complex of FtsB, FtsL and FtsQ (FtsBLQ) is at the heart of the divisome assembly cascade in Escherichia coli. This complex regulates the transglycosylation and transpeptidation activities of the FtsW-FtsI complex and PBP1b via coordination with FtsN, the trigger for the onset of constriction. Yet the underlying mechanism of FtsBLQ-mediated regulation is largely unknown. Here, we report the full-length structure of the heterotrimeric FtsBLQ complex, which reveals a V-shaped architecture in a tilted orientation. Such a conformation could be strengthened by the transmembrane and the coiled-coil domains of the FtsBL heterodimer, as well as an extended beta-sheet of the C-terminal interaction site involving all three proteins. This trimeric structure may also facilitate interactions with other divisome proteins in an allosteric manner. These results lead us to propose a structure-based model that delineates the mechanism of the regulation of peptidoglycan synthases by the FtsBLQ complex. The FtsB-FtsL-FtsQ complex is essential for regulating cell wall synthesis during bacterial cell division. Here, authors report the full-length trimeric structure showing a tilted V-shaped conformation and suggest an allosteric regulatory mechanism.

Automated summary

The FtsB-FtsL-FtsQ complex plays a crucial role in regulating cell wall synthesis during bacterial cell division by mediating the synthesis of the cell-wall peptidoglycan. The full-length structure of the heterotrimeric FtsBLQ complex is reported, showing a tilted V-shaped conformation. This structure may facilitate interactions with other divisome proteins in an allosteric manner, leading to a proposed mechanism for the regulation of peptidoglycan synthases by the FtsBLQ complex.