Fig. 3.

3D-structures of FB self-assemblies. a) Crystal structure FB^SS; b) Crystal structure FB Type I; c) Crystal structure FB Type II. In panel a) though c), each FB subunit is shown with the basic/DNA-binding region in blue (amino acids N-terminal to residue 179), the leucine-zipper region in red or grey (residues 180–214), and the C-terminal region in green (amino acids C-terminal to residue 215). Cys¹⁷² is shown as a yellow sphere. Helix chains are labeled A, B, C, C′, and D, respectively. Interactions between helices that are discussed in the text are labeled (Setting 2, Setting 3, and packing P2 through P5).