Myristoylation of Protein at a Distinct Position Allows Its Phosphorylation by Protein Kinase C

Abstract

A hydrophilic enzyme, lysozyme, was myristoylated in vitro by the N-hydroxysuccinimide ester of myristic acid and three monomyristoylated lysozymes modified at a distinct position (at Lys-13, Lys-33, Lys-97) were isolated by two-step column chromatography. The relationship between membrane binding and phosphorylation by protein kinase C of these monomyristoylated lysozymes were examined using phospholipid vesicles. These three lysozymes bound to phospholipid vesicles to the same extent, whereas the binding of nonmyristoylated native lysozyme was negligible. When native and three monomyristoylated lysozymes were reacted with protein kinase C in a phosphatidylserine (PS)-containing vesicle system, phosphorylation was observed with the myristoylated lysozymes, whereas that of native lysozyme was negligible. However, a remarkable (more than sixfold) difference in the extent of phosphorylation by protein kinase C was observed among three monomyristoylated lysozymes with a different myristoylated position. These results suggest that the membrane binding of substrate protein is not sufficient for the phosphorylation by protein kinase C and the topology of the substrate protein on the membrane play a crucial role in the recognition of substrate protein by protein kinase C. These results further indicate that protein myristoylation can modulate the topology of the membrane-bound protein.