Carbohydrate structures of beta-core fragment of human chorionic gonadotropin isolated from a pregnant individual.
Highly purified beta-core fragment was obtained from urine of a pregnant woman with use of an immunoaffinity column. The amino acid sequence of beta-core fragment indicated that it is composed of two polypeptides linked by a disulfide bond. The two polypeptides correspond to the 6-40 and 55-92 portions of hCG beta-subunit. Both Asn13 and Asn30 residues were glycosylated. The N-linked sugar chains of beta-core fragment were quantitatively released as radioactive oligosaccharides by hydrazinolysis, followed by N-acetylation and NaB3H4 reduction. The radioactive oligosaccharides were fractionated by serial lectin column chromatography and Bio-Gel P-4 column chromatography, and their structures were investigated by sequential exoglycosidase digestion and periodate oxidation. The results indicated that they were a mixture of the four oligosaccharides: Man alpha 1----6(+/- Man alpha 1----3)Man beta 1----4GlcNAc beta 1----4(+/- Fuc alpha 1----6)GlcNAc. The structural characteristics of the sugar chains of beta-core fragment are quite different from those of the beta-subunit of hCG whose structures were typical biantennary sugar chains containing the Neu5Ac alpha 2----3Gal beta 1----4GlcNAc beta 1----2 group as their outer chains.
Endo
T
T
Department of Biochemistry, University of Tokyo, Japan.
Nishimura
R
R
Saito
S
S
Kanazawa
K
K
Nomura
K
K
Katsuno
M
M
Shii
K
K
Mukhopadhyay
K
K
Baba
S
S
Kobata
A
A
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D002240:Carbohydrate Sequence; D006063:Chorionic Gonadotropin / Q000737:chemistry* / Q000652:urine; D002850:Chromatography, Gel; D005260:Female; D006801:Humans; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000032:analysis; D010446:Peptide Fragments / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D011247:Pregnancy / Q000652:urine*
D000596:Amino Acids; D006063:Chorionic Gonadotropin; D009844:Oligosaccharides; D010446:Peptide Fragments