title: Glycogen synthase turnover and phosphorylation in rat H4IIE hepatoma cells.
abstract: Glycogen synthase was isolated from rat H4IIE hepatoma cells by the use of specific antibodies. Immunoprecipitates from cells grown in the presence of [35S]methionine contained two 35S-labeled polypeptides, designated GS1 and GS2, separable by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Labeling of both species was half-maximal after 3 h and remained constant up to 48 h. When cells were incubated with [32P]-phosphate, 32P was incorporated into both species with similar kinetics, half-maximal labeling occurring after 2-3 h. The steady-state ratio 32P/35S was significantly higher for the lower mobility GS2 polypeptide. Pulse-chase experiments showed that the two subunits followed similar kinetics with respect to 35S-labeling. However, the turnover of 32P on the GS2 subunit was significantly faster (t1/2 approximately 30 min) than that on the GS1 subunit (t1/2 approximately 2 h). We suggest that the two polypeptides represent different phosphorylation states of the glycogen synthase subunit and are rapidly interconverted.
authors.affiliation: Department of Biochemistry, Indiana University School of Medicine, Indianapolis 46223.
authors.forename: D J
authors.initials: DJ
authors.lastname: Armstrong
authors.forename: P J
authors.initials: PJ
authors.lastname: Roach
mesh_terms: D000818:Animals; D002460:Cell Line; D006006:Glycogen Synthase / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008114:Liver Neoplasms, Experimental / Q000201:enzymology*; D008970:Molecular Weight; D010766:Phosphorylation; D051381:Rats
chemical_list: D006006:Glycogen Synthase