Binding affinity of N-glycans for aromatic amino acid residues: implications for novel interactions between N-glycans and proteins.

This study advances direct evidence of the binding affinity of N-glycans for aromatic amino acid residues. The intrinsic fluorescence intensities of bovine pancreatic RNase A, bovine alpha-lactalbumin, and aromatic amino acids were markedly depressed in solutions (1 mM or so) of free N-glycans of both the high-mannose and complex types. In addition, free N-glycans inhibited the chemical modifications of the solvent-exposed tyrosine and tryptophan residues of these proteins, confirming the affinity of N-glycans for aromatic amino acid residues. The results are discussed in connection with the roles of N-glycans in novel interactions between N-glycans and proteins.