Structure and function of the Abelson murine leukemia virus transforming gene

The oncogene (v-abl) of A-MuLV is a fragment of a normal mouse gene. Only 1.2 kb on the 5'-end of the v-abl is sufficient to encode a tyrosine-specific protein kinase whose activity is important in transformation. This A-MuLV protein kinase can be active in E. coli and it phosphorylates bacterial proteins. The lack of discrimination in its selection for substrates is puzzling. Because of the demonstration of such promiscuity, the identification of physiologically-relevant phosphorylation events must rely on evidence of functional modification rather than physical modification of proteins.