Synthesis and characterization of the first cysteine-rich domain of novel protein kinase C

The first cysteine-rich domains (CRDʹs) of mouse PKCη and PKCδ (η-CRDl and δ-CRDl) were prepared by automated solid phase peptide synthesis. In the presence of phosphatidylserine, zinc-folded η-CRDl did not bind [3H]phorbol 12, 13-dibutyrate (PDBu) at all while the zinc-folded second CRD of mouse PKCη (η-CRD2) bound PDBu strongly with a Kd of 0.91 nM. Moreover, δ-CRDl showed very weak PDBu binding affinity (Kd = ca.500 nM) while the Kd of the second CRD of mouse PKCδ was reported to be 1.9 nM. These results suggest that the second CRDʹs of PKCη and PKCδ play an important role in the PDBu binding.