Title : A carbohydrate structural variant of MM
glycoprotein (
glycophorin A )
Abstract :
- A variant variant of the MM glycoprotein ( glycophorin A ) was isolated from erythrocyte membranes of two individual donors, a mother (L.G.) and daughter (V.W.)
- This glycoprotein was found to be a carbohydrate variant in which, for both donors, certain O-glycosidically linked saccharides retained the core structure consisting of NeuAc(alpha 2,3)Gal(beta 1,3)GalNAc that is common to all O-linked saccharides of the MN glycoproteins , and, in addition, contained substituents, of varying chain lengths, on the primary carbinol of GalNAc
- These saccharides were released from the polypeptide by beta-elimination in the presence of sodium borohydride, and aspects of their structure were investigated by glycosidase digestion and periodate oxidation
- Thus, the smallest variant structure was deduced to be NeuAc(alpha 2,3)Gal ( beta 1,3 )[ GlcNAc(beta 1,6 )]H2GalNAc
- The 6-O-linked GlcNAc appears to serve as the focus of further chain elongation reactions, involving alternate additions of Gal and GlcNAc residues and leading to the formation of several homologous structures
- Two such structures, NeuAc(alpha 2,3)Gal(beta 1,3)[GlcNAc(beta 1,?
- Gal(beta 1,3/4)GlcNAc(beta 1,6)]H2GalNAc and NeuAc(alpha 2,3) Gal ( beta 1 1,3)[Gal ( beta 1,3 /4)GlcNAc(beta 1,6)]H2GalNAc were the predominant species present
- A larger saccharide was also isolated and its partial sequence was determined to be Gal(beta 1,3/4)GlcNAc(beta 1,?
- [Gal(beta 1,3/4)Glc-NAc(beta 1,?)
- Gal(beta 1,3/4)GlcNAc(beta 1,6)[NeuAc(alpha 2,3)Gal-(beta 1,3)]H2GalNAc
- Because the peptide portion of these glycoproteins contains two methionine residues , it was possible to isolate two CNBr glycopeptides from separate regions of the molecule, and to assess the distribution of these variant structures in the polypeptide
- The saccharides were linked to about 2-3 Ser and/or Thr residues in the donor LG glycoprotein and one of the attachment sites was located within the CNBr glycooctapeptide representing the NH2 terminus
- Considerable heterogeneity in saccharide structure was documented for this site, and it is likely that such heterogeneity occurs also at other sites
- The variant saccharides bear structural similarities to the core region of O-linked saccharides of certain blood group-active mucins and ovarian cyst secretions, and to the outer sequences of N-linked carbohydrate units (I-, i-active) of the major glycoprotein of human erythrocytes, band 3
- The structures of the variant saccharides suggest that they may be potential precursors of H blood group-active carbohydrates, present in varying degrees of maturity, and attached to an integral protein of erythrocytes
Output (sent_index, trigger,
protein,
sugar,
site):
- 0. glycophorin, , glycophorin A, A carbohydrate structural variant, -
- 0. glycoprotein, , glycoprotein, A carbohydrate structural variant, -
- 1. glycoprotein, , glycoprotein, -, -
- 11. glycopeptides, , -, -, glycopeptides
- 11. glycoproteins, , glycoproteins, -, -
- 12. glycoprotein, , glycoprotein, -, -
- 12. linked, , -, The saccharides, Ser
- 12. linked, , -, The saccharides, Thr residues
- 14. glycoprotein, , glycoprotein, N-linked carbohydrate units, -
- 2. glycoprotein, , glycoprotein, a carbohydrate variant, -
- 2. glycoproteins, , glycoproteins, all O-linked saccharides, -
- 3. released, , -, These saccharides, polypeptide
- 4. Gal, , 2,3)Gal, the smallest variant structure, -
Output(Part-Of) (sent_index,
protein,
site):
*Output_Site_Fusion* (sent_index,
protein,
sugar,
site):