title: Procalcitonin is a glycoprotein.
abstract: Messenger RNA extracted from rat medullary carcinoma of the thyroid directs the synthesis in cell-free translation systems of a precursor of calcitonin, Mr = 15,000, substantially larger than the mature form of the hormone, Mr = 3,500. When translations of the mRNA were carried out in the presence of microsomal membranes prepared from a canine pancreas, a larger product (apparent Mr = 17,000) was observed by electrophoresis of the labeled proteins in the translation mixtures on sodium dodecyl sulfate-polyacrylamide gels. This membrane-processed product of Mr = 17,000 was specifically immunoprecipitated by an antiserum to synthetic calcitonin and bound to concanavalin A-Sepharose. Incubation of the proteins synthesized in the cell-free translations performed in the presence of microsomal membranes with the glycosidase, endo-beta-N-acetylglucosaminidase H, reduced the apparent molecular weight of the membrane-processed precursor from 17,000 to 12,000. In addition, the processed Mr = 17,000 calcitonin-related precursor, but not the initial, unprocessed precursor of Mr = 15,000, was resistant to proteolytic digestion by a mixture of trypsin and chymotrypsin. These results indicate that the biosynthesis of calcitonin involves the glycosylation and proteolytic cleavage of a newly synthesized precursor along with sequestration of the processed precursor within microsomal vesicles. Thus, the calcitonin precursor undergoes extensive co- and post-translational processing to the smaller, unglycosylated hormone that is secreted.
mesh_terms: D000818:Animals; D002116:Calcitonin / Q000235:genetics*; D015740:Calcitonin Gene-Related Peptide; D002918:Chymotrypsin; D006023:Glycoproteins / Q000235:genetics*; D008970:Molecular Weight; D009374:Neoplasms, Experimental / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D013964:Thyroid Neoplasms / Q000378:metabolism*; D014357:Trypsin
chemical_list: C000606591:Calca protein, rat; D006023:Glycoproteins; D010446:Peptide Fragments; D011498:Protein Precursors; D012333:RNA, Messenger; D002116:Calcitonin; D002918:Chymotrypsin; D014357:Trypsin; D015740:Calcitonin Gene-Related Peptide