(A) Front view of the E. coli FtsZ structural model. N-and C-terminal domains are represented in brown and gray, respectively. Arrows indicate longitudinal and lateral polymerization axes and the face of FtsZ is described as top, bottom, right and left according to the orientation of GTP (yellow). Residues E83 and R85 locate in the bend within the H3 helix. (B) Primary sequence alignment of the H3 region of FtsZ. The most conserved positions are colored in dark blue. The secondary structure of FtsZ is shown in the last line: alpha helix, orange rectangle; beta strand, blue arrow; coil, grey. The arrows indicate residues E83 and R85 of the E. coli FtsZ sequence.