Identification of procalcitonin in a rat medullary thyroid carcinoma cell line

R. S. Birnbaum, W. C. Mahoney, D. M. Burns, J. A. O'Neil, R. E. Miller, B. A. Roos

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32 Scopus citations


As a first step in studying the biosynthesis of the peptide hormone calcitonin, we have identified procalcitonin species in CA-77 cells, a newly developed rat medullary thyroid carcinoma cell line. mRNA extracted from the cells directed the synthesis of a putative procalcitonin in a reticulocytes lysate translation system containing microsomal membranes. Both this species and a radiolabeled form of immunoreactive calcitonin from intact cells had the same retention time during reverse phase high performance liquid chromatography. The putative cellular procalcitonin was also immunoprecipitated by antiserum to a synthetic peptide whose sequence constitutes the COOH-terminal 16 residues of preprocalcitonin. The polypeptide had a M(r) = 13,400, as estimated by gel filtration chromatography under denaturing conditions. Microsequencing of the [35S]methionine-labeled polypeptide indicated that residues 13, 32, and 34 of procalcitonin were methionine. Similar analysis of the peptide labeled with [3H]proline indicated that residues 2 and 11 of the precursor were proline. The positions of methionine and proline could be aligned in a unique manner with the NH2-terminal half of the preprocalcitonin sequence inferred from cDNA analyses. These results indicate that procalcitonin consists of 111 amino acids and suggest that a 25-residue signal sequence is cotranslationally cleaved from preprocalcitonin. From the procalcitonin sequence we can now predict the sequence of likely biosynthetic intermediates and mature secretory products derived from the NH2-terminal as well as COOH-terminal regions of the precursor.

Original languageEnglish (US)
Pages (from-to)2870-2874
Number of pages5
JournalJournal of Biological Chemistry
Issue number5
StatePublished - 1984
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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