Title : The conformational effects of N-glycosylation on the tailpiece from serum
IgM
Abstract :
- 1H-NMR spectroscopy has been used to study the conformation and dynamics of the isolated tailpiece from human serum immunoglobulin M , a 22-residue peptide containing a single asparagine glycosylation site
- The peptide is isolated as a set of glycoforms, varying only in the sequence of the oligosaccharide attached at the glycosylation site
- The oligosaccharides present have the general formula (Man)n(GlcNAc)2, with 45% having n = 6, 45% having n = 8 and 10% having n = 7 and/or 9
- They have been identified and their NMR parameters compared to those found for the isolated oligosaccharides in free solution
- The conformation and dynamics of the peptide component have also been studied, using NOE data and hydrogen-exchange experiments, and the results compared to those obtained from the aglycosyl peptide of the same sequence
- The presence of the peptide is found to have no measurable effect on the conformation of the oligosaccharides
- However, the presence of oligosaccharide causes a decrease in the conformational mobility of the backbone and sidechains of the peptide in the region of the glycosylation site
- This is proposed to result from interactions between the oligosaccharide core and the amino acid side chains
- Further, the conformation of the N-glycosidic linkage has been shown to be both rigid and planar
- Thus, the conformational space available to an N-linked oligosaccharide in a glycoprotein relative to the protein may depend to a large extent upon the flexibility of the asparagine side chain
- Various roles for the different glycoforms of the tail peptide are discussed