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Topography of glycosylation reactions in the rough endoplasmic reticulum membrane

Journal Article · · J. Biol. Chem.; (United States)
OSTI ID:5491745
;

The translocation of UDP-glucose and GDP-mannose from an external to a luminal compartment has been examined in rat liver vesicles derived from the rough endoplasmic reticulum (RER). RER vesicles with the same topographical orientation as in vivo were incubated with a mixture of (/sup 3/H)UDP-glucose and UDP-(/sup 14/C)glucose to demonstrate that the intact sugar nucleotide was translocated into the lumen of the vesicles. The translocation of UDP-glucose was dependent on temperature and was saturable at high concentrations of the sugar nucleotide. The transfer of glucose to endogenous acceptors was dependent on the translocation of UDP-glucose into the lumen of the RER since leaky vesicles resulted in both a decrease in transport and transfer of glucose to endogenous acceptors. Preliminary results suggest that the mechanism of UDP-glucose transport into RER-derived vesicles is via a coupled exchange with luminal UMP. Using the same experimental approach to detect translocation of UDP-glucose into the lumen of RER vesicles, we were unable to detect transport of GDP-mannose. Incubation of leaky vesicles with GDP-mannose resulted in stimulation of the amount of mannose transferred to endogenous acceptors, in marked contrast to that observed for UDP-glucose and UDP-N-acetylglucosamine. These results suggest that whereas UDP-glucose is translocated across the RER membrane in vitro, GDP-mannose is not transported. In addition, these results tentatively suggest that there is asymmetric synthesis of the lipid-linked oligosaccharides within the membrane of the RER.

Research Organization:
St. Louis Univ. School of Medicine, Mo
OSTI ID:
5491745
Journal Information:
J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 15; ISSN JBCHA
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALDEHYDES
ANIMALS
AROMATICS
AZAARENES
AZINES
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
BIOSYNTHESIS
BODY
CARBOHYDRATES
CELL CONSTITUENTS
CHEMISTRY
DIGESTIVE SYSTEM
ENDOPLASMIC RETICULUM
GLANDS
GLUCOSE
GUANOSINE
HETEROCYCLIC COMPOUNDS
HEXOSES
HYDROXY COMPOUNDS
KINETICS
LABELLED COMPOUNDS
LIVER
MAMMALS
MANNOSE
MEMBRANE TRANSPORT
MONOSACCHARIDES
NUCLEOSIDES
NUCLEOTIDES
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANOIDS
ORGANS
PURINES
PYRIMIDINES
RATS
REACTION KINETICS
RIBOSIDES
RODENTS
SACCHARIDES
SYNTHESIS
TEMPERATURE DEPENDENCE
TRANSLOCATION
TRITIUM COMPOUNDS
URACILS
URIDINE
VERTEBRATES