Figure 13-21


Polypeptide Substrate:

Label Conserved Residues:

Label Inhibitor Target Sequence:

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X-ray structure of the catalytic (C) subunit of mouse protein kinase A (PKA). The protein is in complex with ATP and a 20-residue peptide segment of a naturally occurring protein kinase inhibitor. The N-terminal domain is pink and its C-terminal domain is cyan with its activation loop blue. The polypeptide inhibitor is orange and its pseudo-target sequence, Arg-Arg-Asn-Ala-Ile, is magenta, with the Ala replacing the Ser to be phosphorylated green. The ATP and the phosphoryl group of phosphoThr 197 are shown in space-filling form and the side chains of the catalytically essential Arg 165, Asp 166, and Thr 197 are shown in stick form, all colored according to atom type (C green, N blue, O red, and P orange). Note that the inhibitor's pseudo-target sequence is in close proximity to the ATP's γ phosphate group, the group that the enzyme transfers. [Based on an X-ray structure by Susan Taylor and Janusz Sowadski, University of California at San Diego. PDBid 1ATP.]