Serine carbohydrate chains linked

Figure 4. Structures of the carbohydrate chains linked to protein in Saccharo-myces cerevisiae X2180 mannoprotein. Four types of mannose units are linked to serine (Ser) and threonine (Thr whereas a more complex polysaccharide chain is attached to asparagine (Asn). All anomeric linkages are a, except for the trisaccharide unit l3Man-> fiGNAc- ffGNAc- by which the polysaccharide is linked to asparagine.

Fig. 3. Human CG, hLH, and equine CG (eCG) P-subunits. Amino acid numbeiing is relative to maximum homology between the three subunits. Consensus glycosylation sites ate at Asn-13 and 30. = same amino acid as hCG/3. Underlined Asn residues indicate attachment of N-linked carbohydrate chains. Serines at positions 121, 127, 132, and 138 of hCGP are underlined to indicate sites of O-linked carbohydrate attachment. Residues 115—118,...

Fig. 9. Proposed composite structure showing the relationship of the A, B, H, Le , and Le antigenic determinants of the water-soluble human blood group substances from ovarian cysts. The structure of the side chain in brackets has not been established, but the existence of such a chain is indicated by the mechanism of alkaline borohydride degradation and the oligosaccharides isolated. The carbohydrate chain shown is one of many linked to the serines and threonines of the polypeptide backbone. Chains are not homogeneous and may be of various lengths depending upon genetic composition, incomplete biosynthesis, and unknown factors. From Pereira and Kabat, modified from Lloyd and Kabat cf. Kabat. ...

The 0-glycosically linked carbohydrate chains of fetuin have been cleaved from the protein by alkaline borohydride treatment. Structural analysis revealed the existence of tri- and tetra-saccharides linked 0-glycosidically to L-serine or L-threonine and having structures identical to those previously identified for bovine K-casein and human chorionic gonadotrophin [(27) and (28)]. The A-glycosidically linked chains of fetuin have been assigned structures (36) %r (37). ... 

The third domain, rich in serine and threonine residues, contains eight hydroxy amino acids among 34 residues. This domain may bear clustered 0-linked carbohydrate chains as are found in the corresponding domain in LDL receptor (232). This segment shows the most variation between human and bovine sequence (35). 

Three homogeneous glycoproteins have been isolated from reduced and S -carboxymethylated canine tracheal pouch mucous. Alkaline borohydride reduction indicates that the majority of carbohydrate chains are linked to the protein core by O-glycosidic bonds involving 2-acetamido-2-deoxy-D-galactose residues and either L-serine or L-threonine. 

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