Mechanisms of enhanced binding of natural ligands to lectins. Within individual carbohydrate-binding domains (CRDs), secondary interactions beyond the primary binding site can be with glycan, protein, or lipid portions of glycoconjugate ligands. Multivalent interactions can reflect interaction of single branched oligosaccharides or multiple oligosaccharides attached to a glycoprotein with multiple CRDs brought together within receptor oligomers or in glycan-binding protein (GBP) clusters on the cell surface.