A family of concanavalin A-binding peptides from a hexapeptide epitope library

The lectin concanavalin A (Con A) binds methyl alpha-D-mannopyranoside (Me alpha Man) as well as alpha-D-mannosyl groups at the nonreducing terminus of oligosaccharides. Ligand peptides that mimic the binding of Me alpha Man to Con A were identified from screening an epitope library composed of filamentous phage displaying random hexapeptides. A consensus sequence was identified among affinity-purified phage; Con A binds phage bearing this sequence and is inhibited from doing so by Me alpha Man. When tested for binding against a panel of lectins, phage bearing this sequence bind only weakly to a closely related D-mannose-binding lectin, indicating that binding to Con A is highly selective. A synthetic peptide bearing the consensus sequence blocks the precipitation of Con A by dextran with an inhibition strength equivalent to that of methyl alpha-D-glucopyranoside. These results demonstrate that the specificity of Con A is not limited to carbohydrates and that highly selective sugar-mimics for lectins of plant, animal, or bacterial origin may be identified from epitope libraries.