Structural and functional studies on rabbit liver glycogenin

Glycogenin, the protein primer required for the biogenesis of muscle glycogen, has been isolated from rabbit liver glycogen. The protein comprised 0.0025% of liver glycogen by mass, 200‐fold lower than the glycogenin content of muscle glycogen. Structural analyses, including determination of the amino acid sequence surrounding the glucosylated‐tyrosine residue, showed identity with muscle glycogenin. Catalytically active liver glycogenin was partially purified and, like the skeletal muscle protein, catalysed an intramolecular, Mn²⁺ ‐ and UDP‐Glcdependent autoglucosylation reaction, forming a primer on which glycogen synthase could act. The results demonstrate that hepatic and muscle glycogenins are almost certainly identical proteins and that liver and skeletal muscle share a common mechanism for the biogenesis of glycogen molecules. The results also indicate that there is about one glycogenin molecule/liver glycogen α particle.