Figure 5

Structure of the inhibitor peptide PKI bound to the PKA enzyme: C-terminal region of the substrate. Overall (left) and detail views (right) of the substrate region that lies on the C-terminal side of the phosphorylated serine in complex with the kinase PKA (RCSB Protein Data Bank entry 1JLU [92]) are shown. Ile+1, His+2 and Asp+3 of the PKI substrate as well as the surface of the PKA enzyme to the left are colored according to residue types: white/gray for apolar, green for polar, blue for basic, and red for acidic amino acids. Compared with Figure 3, the orientation of the complex roughly corresponds to a counterclockwise rotation of 90 degrees around the vertical axis. The detail view to the right shows the hydrophobic patch at the surface of PKA which interacts with the substrate residue that lies C-terminally adjacent to the phosphorylated site. The pictures were generated using VMD [93].