Methods for detecting tyrosine kinase-binding target proteins and identifying substances that affect SH2 phosphorylated ligand regulatory systems

A method for identifying a substance that affects a Src homology region 2-phosphorylated ligand regulatory system, comprising:

• (a) contacting a known concentration of peptide comprising a Src homology region 2 domain having the amino acid sequence depicted in SEQ ID NO. 10, SEQ ID NO. 17, SEQ ID NO:18 or SEQ ID NO. 44, a known concentration of phosphorylated ligand and a test substance under conditions which permit the formation of a Src homology region 2-phosphorylated ligand complex;
• (b) measuring the level of complex formed, the level of non-complexed peptide and the level of non-complexed phosphorylated ligand;
• and
• (c) comparing the levels in (b) with the level of complex formed, the level of non-complexed peptide and the level of non-complexed phosphorylated ligand, when the peptide and the phosphorylated ligand are contacted as in (a) but in the absence of test substance, such that a difference in the levels identifies a test substance that affects a Src homology region 2-phosphorylated ligand regulatory system.