title: Phosphorylated variant of bovine prolactin.
abstract: Bovine pituitary explants and cell cultures were incubated with [32P]orthophosphate. Extracts were prepared from the explants and analyzed by sodium dodecyl sulfate-containing acrylamide gel electrophoresis and autoradiography revealing a phosphoprotein that co-migrated with authentic bovine prolactin. Clonal antibodies to bovine prolactin were produced, purified and used to prepare affinity columns. Extracts of [32P]orthophosphate-labeled explants and cells or media were applied to prolactin affinity columns and a radiolabeled protein was eluted with a pH 2.8 wash. The eluted protein was identified as prolactin by co-migration with standard on gel electrophoresis and by amino acid analysis. Treatment of immunoaffinity-purified pituitary prolactin with alkaline phosphatase reduced the phosphate associated with prolactin in a time-dependent manner, indicating a covalent phosphate linkage. Autoradiography of gels revealed prolactin from explants, cells and their associated media to be a phosphoprotein. A phosphorylated variant of bovine prolactin is synthesized and secreted in both explant and cell cultures.
authors.affiliation: Department of Veterinary Pathobiology, Ohio State University, Columbus 43210.
authors.forename: C L
authors.initials: CL
authors.lastname: Brooks
authors.forename: B G
authors.initials: BG
authors.lastname: Kim
authors.forename: P
authors.initials: P
authors.lastname: Aphale
authors.forename: B E
authors.initials: BE
authors.lastname: Kleeman
authors.forename: G C
authors.initials: GC
authors.lastname: Johnson
mesh_terms: D000818:Animals; D001345:Autoradiography; D002417:Cattle; D002478:Cells, Cultured; D002846:Chromatography, Affinity; D004591:Electrophoresis, Polyacrylamide Gel; D014644:Genetic Variation; D010766:Phosphorylation; D010903:Pituitary Gland, Anterior / Q000166:cytology / Q000378:metabolism; D011388:Prolactin / Q000235:genetics / Q000378:metabolism*
chemical_list: D011388:Prolactin