Abstract: The present invention provides methods and kits for identifying interactions between a test compound and a phage-displayed polypeptide, wherein the phage-displayed polypeptide is not a kinase but a protein domain of interest, such as an SH2 domain of interest. The protein domain of interest is displayed on the phage, and the interactions are evaluated in the presence of a reference ligand and in the presence and absence of the test compound.

Abstract: The present disclosure provides a compound screening method comprising screening a test compound that binds a target protein of interest and another ligand protein that is not previously known to form a complex, comprising, (i) in the presence and absence of a test compound, incubating an immobilized ligand protein with a target protein of interest, comprising a nucleic acid tag, wherein the protein of interest and the nucleic acid tag differ from each other; (ii) removing unbound target protein of interest; and (iii) detecting the presence or absence of complex between the immobilized ligand protein, test compound, and the target protein of interest, wherein an increase in the amount of target protein of interest bound to the immobilized ligand protein in the presence of test compound as compared to the absence of test compound indicates the test compound binds to and enables protein-protein complex formation between the immobilized ligand protein and the target protein of interest.