Selection and application of peptide-binding peptides

Peptide-binding ligands would be useful for directing reagents to particular epitopes in a protein, the detection of peptide hormones, and many other applications. Here we show that peptides of modest size isolated from a library using a simple genetic assay can act as specific receptors for other peptides. The equilibrium dissociation constants of these peptide–peptide complexes are higher than those of typical monoclonal antibody–epitope complexes. Nonetheless, as shown here, these peptide-binding peptides can be used to detect or purify proteins containing the partner peptide.