Asb. Edge et Rg. Spiro, STRUCTURE OF THE O-LINKED OLIGOSACCHARIDES FROM A MAJOR THYROID-CELL SURFACE GLYCOPROTEIN, Archives of biochemistry and biophysics, 343(1), 1997, pp. 73-80
A major glycoprotein at the surface of calf thyroid cells, GP-3 (M(r)2
0,000), contains the I-antigenic activity of calf thyroid which has be
en attributed to its poly-N-acetyllactosamine N-linked saccharide chai
ns (Edge, A. S. B., and Spiro, R.G., J. Biol. Chem. 260, 15332-15338,
1985). The present study demonstrated that alkaline borohydride treatm
ent of GP-3 results in the release of five neutral and five acidic sac
charides that were found to represent over 30% of the saccharides of t
his carbohydrate-rich glycoprotein. Three of the oligosaccharides cont
ained terminal alpha 1 --> 3-linked galactose residues which accounted
for their affinity toward Bandeiraea simplicifolia I lectin, The sacc
harides could be grouped into several distinct categories on the basis
of their internal sequence. A novel tetrasaccharide in GP-3 was shown
to have the structure: Gal alpha 1 --> 3Gal beta 1 --> 6(Gal beta 1 -
-> 3)GalNAcH(2). An unsubstituted N-acetylgalactosamine unit and a Gal
beta 1 --> 3GalNAc disaccharide were prominent O-linked constituents,
with the disaccharide serving as a core unit for the attachment of si
alic acid residues to form tetra-and trisaccharides, A branched core s
tructure, Gal beta 1 --> 3(GlcNAc beta 1 --> 6)GalNAcH(2) was shared b
y 4 of the 10 saccharides, the most complete of which was assigned the
sequence NeuAc alpha 2 --> 3Gal beta l --> 3(Gal alpha l --> 3Gal bet
a 1 -->4GlcNAc beta 1 -->6)GalNAcH(2). (C) 1997 Academic Press