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.
Research Article| November 15 1993
Isolation and characterization of phosphorylated bovine prolactin
B G Kim;
Biochem J (1993) 296 (1): 41-47.
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B G Kim, C L Brooks; Isolation and characterization of phosphorylated bovine prolactin. Biochem J 15 November 1993; 296 (1): 41–47. doi: https://doi.org/10.1042/bj2960041
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