Role for the nonessential N terminus of FtsN in divisome assembly

FtsN, the last essential protein in the cell division localization hierarchy in Escherichia coli, has several peculiar characteristics, suggesting that it has a unique role in the division process despite the fact that it is conserved in only a subset of bacteria. In addition to suppressing temperature-sensitive mutations in ftsA, ftsK, ftsQ, and ftsI, overexpression of FtsN can compensate for a complete lack of FtsK in the cell. We examined the requirements for this phenomenon. We found that the N-terminal terminal region (cytoplasmic and transmembrane domains) is critical for suppression, while the C-terminal murein-binding domain is dispensable. Our results further suggest that FtsN and FtsK act cooperatively to stabilize the divisome.