Intramolecular peptide-carbohydrate interactions are potentially important factors in determining glycoprotein structure and function. In this context, we are studying a glycopeptide obtained by tryptic digestion of human serotransferrin consisting of a 21 amino acid polypeptide (G603-R623) with a sialylated biantennary oligosaccharide attached to N611. Having assigned the complete 1H-NMR spectrum of the glycopeptide in H2O, we use primarily two-dimensional {1H-1H} nuclear Overhauser effect spectroscopy (NOESY) as the experimental tool to probe the conformation of the glycopeptide in aqueous solution. We have observed and identified over 280 contacts in the NOESY spectra of the glycopeptide, including a number of remote contacts between sugar and amino acid protons. We have constructed a model structure for the glycopeptide based on distance geometry calculations, restrained by the experimental NOE contacts. 13C Relaxation studies have shown that the mobility of the peptide residues near the glycosylation position is reduced relative to other residues in the extended peptide chain.
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