Identification of amino acid residues required for a specific interaction between Src-tyrosine kinase and proline-rich region of phosphatidylinositol-3' kinase.

The binding of ligand to B-cell antigen receptors (BCR) leads to the activation of receptor-associated Src-family kinases and phosphatidylinositol-3' kinase (PI-3 kinase). Although it has been demonstrated that SH3 domains of several Src-family kinases interact with PI-3 kinase by binding to a proline-rich region of PI-3 kinase in vitro, there is no direct evidence to support their interaction in vivo. Thus, we utilized the yeast two-hybrid assay to reconstitute this protein-protein interaction. This genetic screen clearly indicates that the interaction between SH3 domain of Fyn and the proline-rich region (residues: 80-104) of PI-3 kinase is highly specific. Mutational analysis revealed that amino acid residues Asp92, Tyr93, Arg96 and Thr97 of the SH3 domain of Fyn are essential for interacting with the proline-rich peptide of PI-3 kinase.