Patent ID: 7223547

Claim:
A method of identifying a polypeptide comprising a functional domain of interest comprising: (a) contacting a multivalent recognition unit complex comprising two or more recognition units, with a plurality of polypeptides expressed from a cDNA expression library, in which the recognition units are peptides having in the range 6 to 60 amino acid residues and which selectively bind a domain of interest selected from the group consisting of a catalytic site of glutathione S-transferase (GST), Src homology 1 (SH1), Pleckstrin homology (PH), phosphotyrosine binding (PTB), LIM, armadillo, Notch/ankyrin repeat, zinc finger, leucine zipper, helix-turn-helix and helix-loop-helix; and (b) identifying a polypeptide having a selective binding affinity for said multivalent recognition unit complex; wherein the binding specificity of a recognition unit has been decreased by incorporating said recognition units into said multivalent recognition unit complex, and the identified polypeptide comprises the functional domain of interest.