The modification of onc-proteins with the fatty acid myristate is an early step associated with the transformation of normal to neoplastic cells. The exact significance of myristoylation is transformation has not been established. However, it thought to be part of the mechanism by which cytoplasmic oncogene kinases are localized to the inner plasma membrane surface. Since the transforming activity of onc-kinases is dependent upon this membrane binding, this project will investigate the role of myristoylation as it relates to the mechanism of this subcellular localization. A specific myristoylation assay is being developed using synthetic NH2-terminal polypeptide homologues of celluar and viral myristoylated proteins. The myristyl transferase(s) substrate specificity for polypeptide and fatty acid will be examined in order to define the myristoylation mechanism. The role of covalently bound myristic acid in translocation of myristoylated proteins from their site of cytoplasmic synthesis to the plasma membrane will be examined using mutants of myristoyl-proteins which lack the fatty acid and with myristoyl transferase inhibitors. The involvement of myristic acid in membrane binding will be examined by looking for specific membrane receptors of the myristoyl-proteins. Information on the enzymology of myristoylation and the role of myristic acid in translocation and membrane binding will be used to design and synthesize specific inhibitors of myristoylation in these related phenomena with the goal of developing chemotherapeutic agents specific for a critical early step of malignant transformation.
