title: Golgi galactosyltransferase contains serine-linked phosphate.
abstract: In HeLa and HepG2 cells the Golgi complex enzyme galactosyltransferase became phosphorylated following incubation with 32Pi-Analysis on sodium dodecyl sulphate/polyacrylamide gel electrophoresis revealed incorporation of 32P into the mature 54-kDa form. This phosphorylation was independent of protein synthesis. Serine was identified as the sole phosphorylated amino acid; no radioactive phosphate was detected on N-linked oligosaccharide. The phosphate-labelled galactosyltransferase has the same turnover as [35S]methionine-labelled polypeptides (t1/2 = 20 h). Soluble enzyme, released by the cells, contained very little phosphate relative to that which remained cell-associated. Charge heterogeneity arising from phosphorylation contributes in part to the heterodispersed appearance of the enzyme on two-dimensional gels, as the degree of radioactive phosphate differs among the different iso-enzymes.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002460:Cell Line; D005700:Galactosyltransferases / Q000096:biosynthesis / Q000378:metabolism*; D006056:Golgi Apparatus / Q000201:enzymology*; D006367:HeLa Cells / Q000201:enzymology; D006801:Humans; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism; D010761:Phosphorus Radioisotopes; D010768:Phosphoserine / Q000032:analysis*; D012694:Serine / Q000031:analogs & derivatives*; D013462:Sulfur Radioisotopes
chemical_list: D000596:Amino Acids; D010710:Phosphates; D010761:Phosphorus Radioisotopes; D013462:Sulfur Radioisotopes; D010768:Phosphoserine; D012694:Serine; D008715:Methionine; D005700:Galactosyltransferases