Peptide ligands for a sugar-binding protein isolated from a random peptide library.

Peptide ligands for the carbohydrate-binding protein concanavalin A (Con A) have been identified by screening a large, diverse peptide library expressed on the surface of filamentous phage. A dodecapeptide containing the consensus sequence Tyr-Pro-Tyr was found to bind Con A with an affinity (dissociation constant, Kd) of 46 microM, comparable to that of a known carbohydrate ligand, methyl alpha-D-mannopyranoside (Kd of 89 microM). In addition the peptide inhibited precipitation of the alpha-glucan dextran 1355 by Con A. Given the complexity of oligosaccharide synthesis, the prospect of finding peptides that competitively inhibit carbohydrate-specific receptors may simplify the development of new therapeutic agents.