Fig. 5. FtsN^E binding reduces inhibitory interactions and induces conformational changes observed in SF complexes.

A Conformer of the FtsQLBWIN complex after 1 µs MD, with FtsN^E shown in teal and detailed views of FtsN binding in the Hub region. Highly conserved and essential residues of FtsN, FtsN^W83, FtsN^R84, and FtsN^Y85 are at the AWI interface in the Hub region, close to residues previously identified in the FtsI^R167S SF variant complex, including FtsI^{V86, I168} and FtsL^{L86, N83, A90, E87, L84}. B Dihedral angle analyses of FtsL^G92 (left) and FtsL^H94 (right) in the FtsN-bound complex showed similar backbone dihedral angle changes compared to those in the SF mutant FtsQLBWI^R167S (Fig. 3E). C The distribution of distances between sidechain centers of geometry for FtsL^R67 and FtsI^D225 in the FtsQLBWIN simulation (light gray) exhibited a second, decreased peak compared to that in the FtsQLBWI simulation (dark gray). The distance decrease in FtsQLBWIN occurred with a conformational change in the last 300 ns of the MD simulation (trajectory in Fig. S23), demonstrating tighter packing between the FtsI anchor domain and FtsL in the presence of FtsN. D Interaction between the FtsI anchor-loop residue (magenta) FtsI^Y214 and FtsW^E289 (orange) is disrupted in FtsQLBWIN as FtsI^D225 in the anchor domain increased its interaction with FtsL^R67. This interaction moves the sidechain of FtsI^Y214 (magenta) away from the putative catalytic residue FtsW^D297 (orange), similar to what was observed in the SF complex FtsQLBW^E289GI (Fig. 4D). Note that FtsW^K370 forms a salt bridge with FtsW^D297 in FtsQLBWIN, but not FtsQLBWI. E Ensembles of optimal paths calculated from FtsQ to FtsW^D297 (teal) showing the 10 most optimal paths in the final 500 ns of MD for FtsQLBWI (top left), FtsQLBWI^R167S (top right), FtsQLBWIN (bottom left), and FtsQL^R61EBWI (bottom right). Line colors correspond to the number of paths connecting pairs of residues in the ensemble (colorbar). The DN variant FtsL^R61E (bottom right) eliminated all direct paths between FtsL to FtsW, shifting to paths through a small loop extending from the FtsB helix. Addition of FtsN^E increased the density of paths through FtsI, which also includes paths through the Pivot region. Source data are provided as a Source Data file.