A short peptide is a protein kinase C (PKC) α-specific substrate

The purpose of this study was to find protein kinase C (PKC) isozyme-specific peptides. A peptide library containing 1772 sequences was designed using Scansite and screened by MALDI-TOF MS and kinase activity assays for PKC isozyme-specificity. A peptide (Alphatomega; H-FKKQGSFAKKK-NH ₂) with high specificity for PKCα relative to other isozymes was identified. The peptide was phosphorylated to a greater extent by tissue lysates from B16 melanoma, HepG2, and human breast cancer, which had higher levels of activated PKCα, when compared to normal skin, liver, and human breast tissue lysates, respectively. Moreover, addition of Ro-31-7549, an inhibitor with great specificity for PKCα, to the phosphorylation reaction caused a dose-dependent reduction in phosphorylation, but no inhibition was identified with the addition of rottlerin and H-89. These results show that this peptide has great potential as a PKCα-specific substrate.