Sulfation of porcine parathyroid secretory protein I. Detection of tyrosine sulfate

• Published in: The Journal of biological chemistry Vol. 261; no. 35; pp. 16473 - 16477
• Main Authors: Kumarasamy, R, Cohn, D V
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 15-12-1986; American Society for Biochemistry and Molecular Biology
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Biological and medical sciences; Calcium-Binding Proteins - biosynthesis; Chromogranin A; Chromogranins; Fundamental and applied biological sciences. Psychology; Glycoproteins; In Vitro Techniques; Lysine - metabolism; Parathyroid Glands - metabolism; Proteins; Sulfates - metabolism; Sulfur Radioisotopes; Swine; Tritium; Tyrosine - analogs & derivatives; Tyrosine - analysis; Tyrosine - metabolism; Vertebrata; Mammalia; Parathyroid hormone; Animal; Secretory protein; Glycoproteins; Artiodactyla; Metabolism; Ungulata; Pig; Sulfatation
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(18)66590-1

Secretory Protein I (SP-I) is an acidic glycoprotein that is stored and co-secreted with parathormone by parathyroid glands. It has been found to be chemically similar, if not identical, to chromogranin A of the adrenal medulla and to be present in most endocrine cells. In the present study, 35SO4 was shown to be incorporated into SP-I and several other proteins of porcine parathyroid tissue incubated in vitro. The predominant sulfated species secreted to the medium was SP-I. Up to 20% of the tyrosine residues in secreted SP-I were labeled with 35SO4. Both the cellular and secreted forms migrated on sodium dodecyl sulfate gels as a pair of proteins with apparent molecular weights of 82,000 and 78,000. The 82-kDa protein could be converted to the 78-kDa species by treatment with neuraminidase. Sulfate exists in SP-I as tyrosine sulfate based on the identification of this amino acid by thin layer electrophoresis following alkaline hydrolysis. Extracellular Ca2+ (3 mM) greatly suppressed the secretion of 35SO4-labeled SP-I without affecting the intracellular sulfation of the molecule or the secretion of a minor sulfated protein unrelated to SP-I. The ratio of incorporated 35SO4 to 3H-amino-acid was greater in secreted SP-I than in tissue SP-I, suggesting that much sulfation of this protein occurred during or just before secretion.