title: A 42,000-Da protein in rabbit tissues and in a glycogen synthase preparation cross-reacts with antibodies to glycogenin.
abstract: Rabbit skeletal muscle glycogen previously has been shown to be covalently bound to a 40,000-Da protein ("glycogenin") via a novel glucosyl-tyrosine linkage [I.R. Rodriguez and W.J. Whelan (1985) Biochem. Biophys. Res. Commun. 132, 829-836]. Antibodies raised against rabbit skeletal muscle glycogenin cross-react with a similar protein present in rabbit heart and liver glycogens, as well as with a 42,000-Da "acceptor protein" present in high-speed supernatants of rabbit muscle, heart, retina, and liver. This 42,000-Da protein incorporates [U-14C]Glc when an ammonium sulfate fraction prepared from the tissue supernatants is incubated with UDP-[U-14C]Glc. The [U-14C]Glc incorporated can be removed quantitatively by treatment with amylolytic enzymes, indicating that the [U-14C]Glc incorporation represents elongation of a preexisting glucan attached to the acceptor protein. Furthermore, a commercial preparation of rabbit skeletal muscle glycogen synthase contains this 42,000-Da protein. We propose that the 42,000-Da protein represents the free form of glycogenin in tissues, with its covalently attached glucan chain(s) providing a "primed" elongation site for glycogen synthesis.
mesh_terms: D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005964:Glucosyltransferases; D006006:Glycogen Synthase / Q000378:metabolism*; D006023:Glycoproteins / Q000032:analysis* / Q000378:metabolism; D007118:Immunoassay; D008099:Liver / Q000032:analysis; D008297:Male; D008970:Molecular Weight; D009132:Muscles / Q000032:analysis; D009206:Myocardium / Q000032:analysis; D011817:Rabbits; D012160:Retina / Q000032:analysis; D014532:Uridine Diphosphate Glucose
chemical_list: D006023:Glycoproteins; C051887:glycogenin; D005964:Glucosyltransferases; D006006:Glycogen Synthase; D014532:Uridine Diphosphate Glucose