Serotransferrin glycan, primary structure

Important variations of the plasma serotransferrin concentration are observed in physiological and pathological situations. They are often accompanied by dramatic modifications of glycan primary structure (see section 3.2). 

Fig. 6. Primary structure of serotransferrin diantennary glycans from human (A,B) [211-213], cow (A,B) [119, 214], rabbit (A) [103], sheep (A) [119,215], marsupial (kangaroo, opossum, wallaby) (A) [119,216], Primary structure of human serotransferrin triantennary glycans (C,D) [119-217],...

Fig. 7. Primary structure of the glycans from mouse serotransferrin [119,218,219],...

Fig. 8. Primary structures of the glycans from rat serotransferrin (A,B,C)[221] and from rat mammary gland transferrin (D) [67]. R, GlcNAc(pl-4)[Fuc(al-6)]o- GlcNAc(P-N)Asn.

Fig. 9. Primary structure of the four glycans identified in the three horse serotransferrin variants [113,114,119, 222,223], R, GlcNAc(Pl-4)GlcNAc(pi-N)Asn.

Fig, )0. Primary structure of glycans from fish serotransferrins. A, Carp big-head (Aristichthys nobilis) [224] B, pike Esox lucius)[225]. R, GlcNAc(pl-4)GlcNAc(pl-N)Asn. 

Fig. 16. Primary structure of glycans from turkey ovotransferrin (A) [119,238], hen ovotransferrin (B) [239, 240], chicken embryo serum (C), and chicken serotransferrin (D)[241]. R, GlcNAc(Pl-4)GlcNAc(Pl-N)Asn. Glycans of transferrin from embryo hepatocytes secreted into culture medium are a-l,6-fucosylated.

Human seminal transferrin. Human seminal transferrin (MM 80kDa) contains 6.1% sugars. The primary structure of the major N-linked glycan is identical to that of the serotransferrin diantennary glycan of Fig. 6A [247]. 

Fig. 18. Primary structure of tetra- and pentaantennary glycans from human serotransferrin secreted into culture medium of human hepatocarcinoma cell line Hep G2. The a-l,3-linked fucose residue is conjugated to the GlcNAc of one of the antennae [261]. R, GlcNAc(pi )[Fuc(al-6)]o iGlcNAc(p-N)Asn.

CDG-type II syndrome [265,268] is a separate variant since it is characterized by a severe decrease in the activity of A-acetylglucosaminyltransferase II (UDP-GlcNAc a6-D-mannoside (3-l,2-A-acetylglucosaminyltransferase). As a consequence, the serotransferrin isoforms contain two truncated monoantennary glycans of which the primary structures are described in Fig. 19. 

Fig. 19. Primary structure of the glycan from human serotransferrin isolated from a patient with carbohydrate-deficient syndrome (CDG) type II [265,268], R, GIcNAc(pi-4)GIcNAc(pi-N)Asn.

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