Effects of glycosylation on the conformation and dynamics of O-linked glycoproteins: Carbon-13 NMR studies of ovine submaxillary mucin
- Case Western Reserve Univ., Cleveland, OH (USA)
Carbon-13 NMR spectroscopic studies of native and sequentially deglycosylated ovine submaxillary mucin (OSM) have been performed to examine the effects of glycosylation on the conformation and dynamics of the peptide core of O-linked glycoproteins. OSM is a large nonglobular glycoprotein in which nearly one-third of the amino acid residues are Ser and Thr which are glycosylated by the {alpha}-Neu-NAc(2-6){alpha}-Ga1NAc- disaccharide. The {beta}-carbon resonances of glycosylated Ser and Thr residues in intact and asialo mucin display considerable chemical shift heterogeneity which, upon the complete removal of carbohydrate, coalesces to single sharp resonances. This chemical shift heterogeneity is due to peptide sequence variability and is proposed to reflect the presence of sequence-dependent conformations of the peptide core. These different conformations are thought to be determined by steric interactions of the Ga1NAc residue with adjacent peptide residues. The absence of chemical shift heterogeneity in apo mucin is taken to indicate a loss in the peptide-carbohydrate steric interactions, consistent with a more relaxed random coiled structure. On the basis of the {sup 13}C relaxation behavior the dynamics of the {alpha}-carbons appear to be unique to each amino acid type and glycosylation state. These results are consistent with the changes in molecular dimensions determined by light-scattering techniques for the same series of modified mucins. Taken together, these results further demonstrate that mucins possess a highly expanded conformation that is dominated by steric interactions between the peptide core and the O-linked Ga1NAc residue.
- OSTI ID:
- 5050100
- Journal Information:
- Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 28:13; ISSN 0006-2960; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
62 RADIOLOGY AND NUCLEAR MEDICINE
BODY
CARBOHYDRATES
CARBON 13
CARBON ISOTOPES
CHEMICAL SHIFT
CONFORMATIONAL CHANGES
EVEN-ODD NUCLEI
GLANDS
GLYCOPROTEINS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RESONANCE
SACCHARIDES
SALIVARY GLANDS
SPECTRA
STABLE ISOTOPES