The 36-Kilodalton Substrate of pp60 v- src Is Myristylated in a Transformation-Sensitive Manner

Abstract

A primary intracellular substrate for pp60v-src kinase in a variety of avian and mammalian cells is a protein of 34 to 39 kilodaltons (kD). After incubation of chicken embryo fibroblasts (CEF) with [3H]myristic acid for 4 hours, the 36-kD protein contained covalently bound myristic acid by several criteria: (i) the radioactively labeled material comigrated with the 36-kD protein on sodium dodecyl sulfate-polyacrylamide gels in one and two dimensions, (ii) the labeled material was insoluble in chloroform-methanol, and (iii) radioactively labeled myristate could be recovered from the purified 36-kD protein. The resistance of the acyl fatty acid moiety to hydrolysis by hydroxylamine suggested that the covalent linkage to the 36-kD protein may be through an amide linkage. The [3H]myristic-acid labeling of the 36-kD protein in Rous sarcoma virus-transformed CEF showed a reduction of up to 45 percent when compared to an identical amount of 36-kD protein derived from normal cells; this reduction was not due to general changes in myristic acid metabolism in transformed cells.