Structure of Bacillus subtillis FtsZ. A, Ribbon diagram of the non-crystallographic dimers viewed approximately parallel to the NCS 2-fold axis is shown. Bound GDP within the active site is represented in stick drawing. B, The Fo-Fc omit electron density map contoured at 3σ is shown in blue. Stick representation of bound GDP is modeled in the omit density. C, Hydrogen bond interactions between FtsZ active site residues (stick) and GDP (ball and sticks) are shown as black dashed lines. Amino acids residues are numbered and the FtsZ backbone is shown in grey.