Protein kinase inhibitor Gamma is a member of the PKA inhibitor family. Studies of a similar protein in mice suggest that this protein acts as a potent competitive PKA inhibitor, and is a predominant form of PKA inhibitors in various tissues. Three alternatively spliced transcript variants encoding the same protein have been reported.Most of the amino acid residues in the domain of PKI-gamma that showed affinity for the catalytic subunit are conserved, and PKI-gamma also has a region highly similar to the consensus PKI nuclear export signal. Northern blot analysis detected a 1.3-kb transcript in all tissues examined, with highest expression in heart, skeletal muscle, and testis. The authors verified the presence of PKI-gamma protein in mouse tissues by purifying it from heart using DEAE chromatography.