Core conserved residues shared by the entire superfamily and the conformational changes associated with the helical subdomain. (a) cAMP bound structure of the PKA regulatory subunit R1alpha (PDB: 1RGS). (b) Catalytic subunit (C-subunit) bound structure of R1alpha (PDB: 2QCS). The alpha subdomain is shown in yellow and the beta subdomain is shown in white. The PBC region is colored in red. The hydrophobic residues are shown in sticks and surface representation, and the glycine residues are shown in CPK representation. The core conserved residues are colored in gold.