Sequence-Specific Peptide-Carbohydrate Interactions in an Asparagine-Linked Glycopeptide

摘要

Asparagine glycosylation (N-glycosylation) of the Asn-Xaa-Ser/Thr sequence is a cotranslational process that can affect protein structure and function. Little is known, however, about glycosylation's influence on the structure of flexible N-glycopeptides. Fluorescence studies show that N-glycosylation can alter peptide backbone conformation. Circular dichroism also indicates that N-glycosylation can perturb α-helical structure. In this work, we use NMR to determine details about N-glycopeptide structure in an organic solvent. Significantly, glycopeptide Ac-Asn(β1-N-GlcNAc)Leu-Thr-NH_2 (1) shows long-range ~1H-~1H NOEs between the peptide and the N-acetylglucosamine (GlcNAc) sugar attached to Asn1. Besides these peptide-sugar NOEs, a comparison of ~3J_(α,β) coupling constants and NH temperature coefficients in glycopeptide 1 and aglycosyl peptide Ac-Asn-Leu-Thr-NH_2 3 indicate that N-glycosylation stabilizes peptide conformation.