Sulfation of porcine parathyroid secretory protein I. Detection of tyrosine sulfate.
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.
D000818:Animals; D002135:Calcium-Binding Proteins / Q000096:biosynthesis*; D053379:Chromogranin A; D002864:Chromogranins; D066298:In Vitro Techniques; D008239:Lysine / Q000378:metabolism; D010280:Parathyroid Glands / Q000378:metabolism*; D013431:Sulfates / Q000378:metabolism*; D013462:Sulfur Radioisotopes; D013552:Swine; D014316:Tritium; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism
D002135:Calcium-Binding Proteins; D053379:Chromogranin A; D002864:Chromogranins; D013431:Sulfates; D013462:Sulfur Radioisotopes; D014316:Tritium; C005662:tyrosine O-sulfate; D014443:Tyrosine; D008239:Lysine