1H NMR studies of the effects of glycosylation on the C-terminal pentapeptide of peptide T.

The C-terminal pentapeptide of peptide T (T5) and a glycosylated analogue (T5GlcNAc) were investigated using 1H NMR spectroscopy to examine the influence of the sugar on the secondary structural characteristics of the peptide. The NMR data confirm the presence of a turn structure amongst an ensemble of predominantly randomly structured species in a solution of 83% TFE/H2O for both peptides. This is in agreement with a previous CD analysis demonstrating the presence of beta-turn. Unlike the CD study, the NMR data do not show a difference in the time-averaged conformation of the glycosylated versus non-glycosylated peptide. These studies suggest that any sugar-peptide interactions which occur in this system are transient in nature, and that they do not greatly influence the local secondary structural characteristics of the peptide. In particular, the turn predisposition already exhibited by the peptide appears to be neither enhanced nor reduced by a neighbouring natural N-glycosylation site. This finding is likely to be of general interest, given the importance of glycosylation as a post-translational modification and that its role in determining protein structure has yet to be characterized.