FIG. 5.

The conserved kinase domain. The catalytic domain of protein kinase A (PKA) includes a kinase core flanked by two tails: the N-terminal tail and the C-terminal tail. The kinase core is a signature of the eukaryotic kinase superfamily and has a characteristic bi-lobal structure. ATP binds in the cleft between the two lobes while the substrate peptide binding region is localized to the C-lobe. Two lobes of the kinase core are connected by a network of hydrophobic residues assembled into two “spines.”