Fig. 2.

Comparison of the inactive (Left) and the active forms of CAP (Right). (A) Schematic representation of CAP shows β-strands as arrows and α-helices as coils. The cAMP is shown in ball and stick representation. DNA is shown as transparent spheres and its bases are colored slate blue. (B) The cAMP binding domains and DNA have been excluded to emphasize the orientations of the DNA binding domains and the C-helices. Residues capping the C- and D-helices and cAMP are shown as ball and stick. In the inactive form, K130 is located at the C termini of the C-helices, whereas in the active form, D138 is located at the N termini of the D-helices. (C) The C terminus of the C-helix, the N terminus of the D-helix, and the hinge residues of one protomer of the inactive and the active form.