title: Isolation and characterization of phosphorylated bovine prolactin.
abstract: Quantitative isolation of bovine prolactin was accomplished by immunoaffinity chromatography using clonal antibody as the stationary ligand. The phosphorylated and non-phosphorylated (native) prolactins contained in the immunopurified preparations were separated by chromatofocusing. Isolates from individual pituitaries revealed that phosphorylated prolactin represented between 20 and 80% of the total prolactin. The stoichiometry of phosphate in phosphorylated prolactin was 1.4:1 when determined by amino acid analysis after preparation of the S-ethylcysteine derivative. One major phosphorylation site, serine-90, and two minor sites, serine-26 and -34, were determined by mapping and sequencing studies. Serine-90 was conserved in prolactins, growth hormones and placental lactogens. Serine-26 and -34 were conserved in prolactins, but were not found in growth hormones or placental lactogens. Absorption spectroscopy of the aromatic amino acid residues indicated that phosphorylation of prolactin was associated with a unique structural conformation.
authors.affiliation: Department of Veterinary Pathobiology, Ohio State University, Columbus 43210.
authors.forename: B G
authors.initials: BG
authors.lastname: Kim
authors.forename: C L
authors.initials: CL
authors.lastname: Brooks
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000302:isolation & purification; D002417:Cattle; D002846:Chromatography, Affinity; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D013006:Growth Hormone / Q000737:chemistry; D006801:Humans; D007074:Immunoglobulin G / Q000302:isolation & purification; D051379:Mice; D008807:Mice, Inbred BALB C / Q000276:immunology; D008969:Molecular Sequence Data; D009924:Organ Culture Techniques; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010449:Peptide Mapping; D010710:Phosphates / Q000378:metabolism*; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010903:Pituitary Gland, Anterior / Q000737:chemistry / Q000378:metabolism*; D010928:Placental Lactogen / Q000737:chemistry; D011388:Prolactin / Q000737:chemistry* / Q000302:isolation & purification* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine
chemical_list: D000911:Antibodies, Monoclonal; D007074:Immunoglobulin G; D010446:Peptide Fragments; D010710:Phosphates; D010768:Phosphoserine; D012694:Serine; D011388:Prolactin; D013006:Growth Hormone; D010928:Placental Lactogen