Intracellular glycosylation of vitellogenin in the liver of estrogen-stimulated Xenopus laevis

Journal Article · Thu Dec 31 23:00:00 EST 1981 · J. Biol. Chem.; (United States)

OSTI ID:5639699

Gottlieb, T A ^[1]; Wallace, R A

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1. University of Tennessee-Oak Ridge Graduate School of Biomedical Sciences

Pulse-chase experiments measuring the rates of incorporation of radiolabeled glucosamine and galactose into intracellular vitellogenin show that glycosylation of this multicomponent protein occurs in a Golgi-enriched fraction isolated from homogenized liver slices. No apparent role of the rough endoplasmic reticulum in this process was demonstrable. Kinetics of the intracellular translocation of glycosylated vitellogenin indicate that the galactosylated intermediate is secreted more rapidly than the glucosamine-labeled precursor. This was corroborated by measuring the rates of accumulation of various pulse-labeled forms of vitellogenin in the chase medium. In addition, a negligible amount of mannose was incorporated into intracellular or secreted vitellogenin. The antibiotic tunicamycin was shown to inhibit (/sup 3/H) glucosamine incorporation into microsomal vitellogenin by 70% without any significant effect on the synthesis of the protein backbone. In addition, nonglycosylated vitellogenin showed normal secretion kinetics. After suitable pretreatment with the antibiotic followed by a labelling period in tunicamycin-free medium, mannose was still not incorporated into vitellogenin, whereas glucosamine behaved in a typical manner. In contrast to this finding, gas-liquid chromatography of the alditol acetate derivatives of the neutral hexoses of vitellogenin showed that mannose was indeed a major component of the vitellogenin oligosaccharide side chain. These preliminary results indicate that the oligosaccharide component of vitellogenin in Xenopus laevis is a ''complex'' type of carbohydrate unit which is linked via an N-glycosidic bond between an asparagine residue and N-acetylglucosamine. With respect to the subcellular localization of glycoprotein assembly in Xenopus liver, there is a significant departure from currently accepted models of glycoprotein synthesis.

• DOE Contract Number: W-7405-ENG-26
• OSTI ID: 5639699
• Journal Information: J. Biol. Chem.; (United States), Journal Name: J. Biol. Chem.; (United States) Vol. 257:1; ISSN JBCHA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALDEHYDES
AMINES
AMPHIBIANS
ANIMALS
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
AQUATIC ORGANISMS
BIOSYNTHESIS
BODY
CARBOHYDRATES
DIGESTIVE SYSTEM
DRUGS
ESTROGENS
FROGS
GALACTOSE
GLANDS
GLUCOPROTEINS
GLUCOSAMINE
HEXOSAMINES
HEXOSES
HORMONES
INHIBITION
LABELLED COMPOUNDS
LIVER
MANNOSE
MOLECULAR STRUCTURE
MONOSACCHARIDES
ORGANIC COMPOUNDS
ORGANS
PROTEINS
RESPONSE MODIFYING FACTORS
SACCHARIDES
STEROID HORMONES
STIMULATION
SYNTHESIS
TRANSLOCATION
TRITIUM COMPOUNDS
UPTAKE
VERTEBRATES