Fig. 5: The FtsZ N-IDR acts via competing interactions.

a FtsZ may polymerize into proper-sized (middle column, wild-type), undersized (left, weakened assembly), or oversized (right, strengthened assembly) entities at protein (top row), protofilament (middle), and subcellular (bottom) levels. b A structure model showing that residue K51 in one subunit interacts with E3 or P203 in a neighboring subunit as suggested by a mass spectrometry analysis of in vivo photocrosslinked products as shown in Supplementary Tables 1, 2; the structure model was based on threading the E. coli FtsZ sequence through one of the S. aureus crystal structures in the tense conformation for amino acids 11–315 (PDB:3VOA) and hand-drawn for amino acids 1–10. c Immunoblot showing photocrosslinked FtsZ^K51Bpa products in cells expressing FtsZ-pdt, which was degraded when proteinase mf-Lon was induced; molecular weight marker positions and FtsZ forms are indicated on the right and left, respectively. d MS/MS spectrum and schematics showing the identification of peptide fragments crosslinked with K51Bpa in FtsZ^ΔNIDR; B, Bpa. e Functional complementation analysis results of FtsZ^ΔNIDR-P203S and FtsZ^P203S. f Coomassie brilliant blue staining shows sedimentation fractions containing polymerized FtsZ forms with a starting monomeric concentration of 3 μM and 2 mM of GTP; T total, S supernatant, P pellet. g Statistically relative FtsZ proportions in pellets, as analyzed in (f); n = 3; mean ± SEM; parametric unpaired two-tailed Student’s t-test, ***P < 0.001, n.s.no significance; P values for the different parameters are: FtsZ^WT-FtsZ^D10F = 0.0005; FtsZ^WT-FtsZ^∆NIDR = 0.0001. h Timelapse images (brightfield, fluorescence, and merged) showing ftsZ-ΔNIDR-P203S-mneongreen cells; scale bar = 2 μm. i Five heat maps depicting the mean smallest distance between the N-IDR of one FtsZ subunit and the N-domain of its neighboring subunit, each representing the last 50 ns from an independent 150 ns molecular dynamics simulation (top row). Five average conformations of the FtsZ dimer structure based on the last 50 ns of each simulation are displayed (middle row). Five heat maps depicting the mean smallest distance between the N-IDR (residues 1–10) or the T7 loop (residues 198–211) of one FtsZ subunit, and the N-domain (residues 42–54) of its neighboring subunit during the last 50 ns of each simulation are displayed (bottom row). For comparison, the initial conformation (prior to energy minimization and subsequent steps) is also presented. j Schematic showing the interaction-modulating mechanism for Z-ring assembling. Source data of c, d, f, g, i are provided in the Source Data file.