This peptide is a potent and competitive inhibitor of protein kinase A (PKA) with a Ki = 1.7 nM. The peptide sequence corresponds to residues 6-22 of human cAMP-dependent protein kinase inhibitor alpha (PKI-alpha) and is amidated at the C-terminus end. PKI-alpha interacts with the catalytic subunit of PKA after the cAMP-induced dissociation of its regulatory chains.Thr-Tyr-Ala-Asp-Phe-Ile-Ala-Ser-Gly-Arg-Thr-Gly-Arg-Arg-Asn-Ala-Ile-NH2 or TYADFIASGRTGRRNAI-NH2