THE INTERACTION OF MYRISTYLATED PEPTIDES WITH THE CATALYTIC DOMAIN OFPROTEIN-KINASE-C REVEALED BY THEIR SEQUENCE PALINDROMY AND THE IDENTIFICATION OF A MYRISTYL BINDING-SITE

Using a model of the enzyme structure and the results from a series of free and myristylated peptides, we provide evidence that peptides cor responding to the pseudosubstrate sequence of protein kinase C bind to the enzyme substrate binding site in an essentially extended conforma tion. This and the nearly symmetrical location of positive charges aro und the substrate phosphoritable site allow the peptide to bind to the enzyme in either an N-to-C orientation or its C-to-N opposite orienta tion. The latter is favoured by a change in residue chirality or when the peptide bears a myristoyl chain at its N-terminus. A myristyl bind ing site was also identified in the enzyme structure and its location in a region proximal to the C-terminal residue of pseudosubstrate boun d in the N-to-C direction suggested that C-myristylation of peptide su bstrates should be more effective than N-myristoylation in antagonizin g the enzyme. A peptide (H-RFARKGALRQKN-CONH-Myr) which contains the m yristyl chain covalently linked to the C-terminal residue of the pseud osubstrate was thus made and shown to be a potent inhibitor of the his tone kinase reaction of protein kinase C and the phosphorylation of p4 7 in intact cells.