Carbohydrate microheterogeneity of rat serotransferrin. Determination of glycan primary structures and characterization of a new type of trisialylated diantennary glycan.
A previously established procedure [Regoeczi, E., Chindemi, P.A., Rudolph, J. R., Spik, G. & Montreuil, J. (1987) Biochem. Cell Biol. 65, 948-954] was used to isolate from three DEAE-cellulose chromatographic fractions of diferric rat serotransferrin (rTf) subpopulations having discernible affinities for concanavalin A (ConA). These entities are designated rTf-1 (not retarded by ConA column), rTf-2 (retarded) and rTf-3 (bound). Each rTf type was found to be endowed with carbohydrate sufficient to account for a single diantennary glycan/protein molecule. Glycan structures were determined on the glycopeptides by employing GLC/MS and 400-MHz 1H-NMR spectroscopy. All glycans possessed a common, trimannosyl-N,N'-diacetylchitobiose core with or without one L-fucose alpha-1,6-linked to the Asn-linked GlcNAc. However, there were differences in the antennae. Thus, in rTf-3, both antennae were of the disialylated diantennary N-acetyllactosamine type which is frequently encountered in other plasma glycoproteins. However, the alpha-1,3-Man-linked antenna in rTf-1 as well as rTf-2 had the sequence: Neu5Ac(alpha 2-3)Gal(beta 1-3)[Neu5Ac(alpha 2-6)]GlcNAc(beta 1-2)Man. In addition, the alpha-1,6-Man-linked antenna deviated in rTf-2 from the standard structure by having the sequence: Neu5Ac(alpha 2-3)Gal(beta 1-3)GlcNAc(beta 1-2)Man. The possible relevance of the above structures to the ConA binding of rTf is discussed. A further preparation, obtained from the most anionic DEAE-cellulose fraction (peak V) or rTf contained several tetrasialylated diantennary glycans whose precise structures remain to be established in future studies.
Spik
G
G
Laboratoire de Chimie Biologique, Université des Sciences et Techniques de Lille Flandres-Artois, Villeneuve d'Ascq, France.
Coddeville
B
B
Strecker
G
G
Montreuil
J
J
Regoeczi
E
E
Chindemi
P A
PA
Rudolph
J R
JR
D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002848:Chromatography, DEAE-Cellulose; D003208:Concanavalin A / Q000378:metabolism; D006020:Glycopeptides / Q000032:analysis; D006859:Hydrogen; D009682:Magnetic Resonance Spectroscopy; D008745:Methylation; D008969:Molecular Sequence Data; D011134:Polysaccharides / Q000737:chemistry*; D051381:Rats; D014168:Transferrin / Q000737:chemistry* / Q000378:metabolism
D006020:Glycopeptides; D011134:Polysaccharides; D014168:Transferrin; D003208:Concanavalin A; D006859:Hydrogen