JBC, Vol. 250, Issue 24, 9283-9293, Dec, 1975
Glycoprotein biosynthesis in plants. Demonstration of lipid-linked oligosaccharides of mannose and N-acetylglucosamine
W. T. Forsee and A. D. Elbein
Previous studies from this laboratory have shown that particulate
preparations from maturing cotton fibers catalyze the transfer of mannose
from GDP-[14C]mannose into mannosylphosphorylpolyisoprenol (Forsee, W. T.,
and Elbein,A. D. (1973) J. Biol. Chem. 248, 2858-2867). In this report, we
show that these particulate preparations also catalyze the inocoporation of
mannose from GDP-[14C]mannose into lipid-linked oligosaccharides and into
glycoprotein. The oligosaccharide-lipids were treated with dilute acid to
liberate the water-soluble oligosaccharides and these oligosaccharides
could then be separated into seven or eight distinct radioactive peaks by
paper chromatography in isobutyric acid/NH4OH/H2betaO (57/4/39). The
smallest of the oligosaccharides appears to be a trisaccharide with the
structure Man leads to GlcNAc-GlcNAc. Thus the oligosaccharides attached to
the lipids apparently range in size from those having 3 glycose units to
those having approximately 8 to 10 glycose units. The radioactivity in the
smaller-sized oligosaccharide-lipids could be chased into the larger
oligosaccharide-lipids by a second incubation in the presence of unlabeled
GDP-mannose. The sugar at the reducing ends of the oligosaccharides was
identified as GlcNAc while some mannose (20 to 30%) was present in alpha
linkages at the nonreducing ends...
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