Fig. 7. Lithostathine protofibril. Reconstructed image of a lithostathine protofibril obtained as described in Results. (A) View of the protofibril axis and section. Electrostatic interactions involving acidic residues (in red) and basic residues (in blue) are shown (top). Four helices (green, red, blue or yellow) form the protofibril with seven monomers per turn (bottom). The helix pitch is 18 nm. Eight tetramers are shown. A rotation of 52° was applied between each tetramer of lithostathine after energy minimization. The diameter of the protofibril is 10 nm. (B) Same view as in (A) but with β-sheets only. Hydrophobic β-sheets corresponding to 24–33 and 136–143 regions are shown in red, the other in yellow. (C) Same view as in (A) but with α-helices only. H2 (in blue) is perpendicular to the protofibril axis, whereas H3 (in green) is parallel.