Analysis of specific interactions of synthetic glycopolypeptides carrying N-acetyllactosamine and related compounds with lectins

Analysis of interactions of synthetic glycopolypeptides with lectins was performed with a biosensor based on surface plasmon resonance (SPR). A series of synthetic oligosaccharide-substituted poly(l-glutamic acid)s were immobilized on sensor surfaces via the γ-carboxyl groups of their peptide moieties by the surface thiol coupling method. Artificial glycopolypeptides: an N-acetyllactosamine-substituted polymer (1), an N-acetylisolactosamine-substituted polymer (2), a (GlcNAc)3-substituted polymer (3), a (GlcNAc)2-substituted polymer (4), and a p-aminophenyl N-acetyl-β-lactosaminide-substituted polymer (5), were used as the ligands. On analysis by SPR, surface-bound polymers 1 and 5 reacted with Erythrina cristagalli agglutinin (ECA), Lycopersicon esculentum agglutinin (LEA), Ricinus communis agglutinin-120 (RCA120), and wheat germ (Triticum vulgaris) agglutinin (WGA). Polymer 2 reacted with WGA and RCA120, but did not with ECA and LEA. The results indicate that β-(1⃗4)-linked galactosyl residues are needed for binding to ECA and LEA. Polymer 3 reacted strongly with LEA and WGA, but polymer 4 reacted strongly only with WGA. Affinity constants (KA) for surface-bound polymer 5–lectin interactions were also about 4–61 times as strong as those for surface-bound polymer 1–lectin interactions. These artificial glycopolypeptides were shown to be useful as tools and probes of carbohydrate recognition and modeling in the analysis of glycoprotein–lectin interactions.