The many faces of Src: multiple functions of a prototypical tyrosine kinase

c-src was first isolated as the normal cellular homologue of v-src, the transforming gene of Rous Sarcoma virus (Stehelin et al., 1976). As the first proto-oncogene described and one of the first molecules demonstrated to have tyrosine kinase activity, Src has provided a prototype for understanding signal transduction involving tyrosine phosphorylation. Comparison between c-src and activated or transforming mutants of Src including v-src, combined with recent data on the structure of Src family kinases has provided new insight into their regulation. In this review, I will discuss the function of the various domains of Src in light of these mutational and structural studies.