A self-glycosylating protein is the primer for rabbit muscle glycogen biosynthesis

J. Lomako, W. M. Lomako, William J. Whelan

Research output: Contribution to journalArticle

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Abstract

In this paper we elucidate part of the mechanism of the early stage of the biosynthesis of glycogen. This macromolecule is constructed by covalent apposition of glucose units to a protein, glycogenin, which remains covalently attached to the mature glycogen molecule. We have now isolated, in a 3500-fold purification, a protein from rabbit muscle that has the same M(r) as glycogenin, is immunologically similar, and proves to be a self-glycosylating protein (SGP). When incubated with UDP-[14C]glucose, an average of one molecular proportion of glucose is incorporated into the protein, which we conclude is the same as glycogenin isolated from native glycogen. The native SGP appears to exist as a high-molecular-weight species that contains many identical subunits. Because the glucose that is self-incorporated can be released almost completely from the acceptor by glycogenolytic enzymes, the indication is that it was added to a preformed chain or chains of 1,4-linked α-glucose residues. This implies that SGP already carries an existing maltosaccharide chain or chains to which the glucose is added, rather than glucose being added directly to protein. The putative role of SGP in glycogen synthesis is confirmed by the fact that glucosylated SGP acts as a primer for glycogen synthase and branching enzyme to form high-molecular-weight material. SGP itself is completely free from glycogen synthase. The quantity of SGP in muscle is calculated to be about one-half the amount of glycogenin bound in glycogen.

Original languageEnglish
Pages (from-to)3097-3103
Number of pages7
JournalFASEB Journal
Volume2
Issue number15
StatePublished - Dec 1 1988

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Biosynthesis
Glycogen
glycogen
Muscle
rabbits
biosynthesis
Rabbits
Muscles
muscles
Glucose
glucose
Proteins
proteins
glycogen (starch) synthase
Glycogen Synthase
Muscle Proteins
1,4-alpha-Glucan Branching Enzyme
Molecular Weight
Uridine Diphosphate Glucose
molecular weight

ASJC Scopus subject areas

  • Agricultural and Biological Sciences (miscellaneous)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Biochemistry
  • Cell Biology

Cite this

A self-glycosylating protein is the primer for rabbit muscle glycogen biosynthesis. / Lomako, J.; Lomako, W. M.; Whelan, William J.

In: FASEB Journal, Vol. 2, No. 15, 01.12.1988, p. 3097-3103.

Research output: Contribution to journalArticle

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