Figure 4.

Average percentage of helicity of (A) two-helix bundle and (B) straight helix: the N-terminal region (residues 2–23: red), helix-turn-helix (HTH) motif (residues 20–60: black), and the C-terminal region (residues 57–83: blue). Helicity is measured based on the number of hydrogen bond between N−H (i) and C=0 (i+4) of backbone. A hydrogen bond (D−H⋯A) is defined by the H⋯A distance <2.8 Å and the D−H⋯A angle >120°.