Src as a Target for Pharmaceutical Intervention

Src is a nonreceptor type protein tyrosine kinase and a prototype of a family consisting of eight members in vertebrates: Src, Yes, Fyn, Fgr, Lyn, Hck, Lck, Blk. Src is an evolutionary well-conserved gene in vertebrates with homologs expressed in invertebrates. When compared with other nonreceptor type 1 tyrosine kinases in the human genome, the Src family is the largest, with its members very closely related to each other, particularly those within two Src family subgroups (Fig. 1). Such a high degree of similarity is also present in receptor tyrosine kinase families, e.g., the epidermal growth factor receptor (EGFR) family, which is the most similar to nonreceptor tyrosine kinases (Fig. 1). Interestingly, the presence of many close family members within the Src family corresponds to their biological activity, which is linked to physical and functional association with receptor tyrosine kinases at the plasma membrane (1).