FIG 2 .

FtsZ^G193D produces twisted and shorter polymers. (a) MD simulations of dimers of S. aureus FtsZ^WT (PDB code 3VO8) and FtsZ^G193D reveal a propensity for twist in FtsZ^G193D dimers. Simulations were initialized as straight dimers at t = 0 (side view). The top view highlights the development of twist between the principal axes of the two FtsZ^G193D subunits at t = 50 ns. (b) Shown are filaments of 14 subunits constructed by extrapolating the dimer interface from time points during the MD simulations. The FtsZ^WT dimer bent but remained untwisted for the first ~100 ns. (c) The FtsZ^G193D dimer rapidly adopted a substantial degree of twist, while the FtsZ^WT dimer acquired twist much later in the simulation. (d) Snapshots at the beginning and end of the FtsZ^WT dimer simulation, in which residues are colored if they interact (defined as being within 5 Å of another residue) with the opposite subunit at any point during the simulation. Colors: orange, specific to the nontwisted state of the wild type, with an interaction in the first 100 ns and no interaction after 150 ns (and no interaction throughout the FtsZ^G193D simulation); purple, generally present in twisted states (always interacting in FtsZ^G193D and after 150 ns for FtsZ^WT); pink, specific to FtsZ^G193D. The salt bridge between Asp97 (light green) and Arg67 (cyan) became broken at t = 262 ns. Gly193 is dark green. (e) Polymers of S. aureus FtsZ^WT (left) and FtsZ^G193D (right) imaged by transmission electron microscopy (TEM). Scale bar: 100 nm. (f) Measurements of FtsZ^WT and FtsZ^G193D polymer (n >70) lengths in the TEM images show that FtsZ^G193D polymers are significantly shorter than FtsZ^WT polymers (P < 0.0001).