Breaking the limits in analyzing carbohydrate recognition by NMR: Resolving Branch-Selective Interaction of a Tetraantennary N-Glycan with lectins

The biological recognition of complex-type N-glycans is part of many key physiological and pathological events. Despite their importance, the structural characterization of these events remains an unsolved task. The inherent flexibility of N-glycans hampers crystallization and the chemical equivalence of individual branches precludes their NMR characterization. By using a chemoenzymatically synthesized tetraantennary N-glycan conjugated to a lanthanide binding tag, the NMR signals under paramagnetic conditions discriminated all four N-acetyl lactosamine antennae with unprecedented resolution. The NMR data revealed the conformation of the N-glycan and permitted for the first time the direct identification of individual branches involved in the recognition by two N-acetyllactosamine-binding lectins, Datura stramonium seed lectin (DSL) and Ricinus Communis agglutinin (RCA120).We thank Agencia Estatal de Investigacion and MINECO of Spain (Grants CTQ2016-76263-P, CTQ2015-64597-C2-1P, CTQ2015-64597-C2-2P, CTQ2015-64624-R and the SEV-2016-0644 Severo Ochoa Excellence Acreditation) and the Deutsche Forschungsgemeinschaft for financial support