title: Evidence for a signal sequence at the N terminus of the common precursor to adrenocorticothrophin and beta-lipotropin in mouse pituitary cells.
abstract: The precursor to corticotropin and beta-endorphin was synthesized in a reticulocyte cell-free system under the direction of mRNA from mouse AtT-20 pituitary tumor cells in the presence of [3H]proline, [3H]phenylalanine, [3H]leucine, [3H]valine, [3H]isoleucine or [35S]methionine. Automatic Edman degradation of the radioactive cell-free product showed the following N-terminal sequence: Pro-1, Met-2, Leu-11, Leu-12, Leu-13, Leu-15, Leu-16, Leu-17, Ile-21 and Val-23. The corticotropin-endorphin precursor was also labeled in AtT-20 cells with [3H]valine, [3H]leucine, [3H]tryptophan, [3H]serine, [35S]methionine or [35S]cysteine. Automatic Edman degradation of the radioactive intact cell form gave the following N-terminal sequence: Trp-1, Cys-2, Leu-3, Ser-5, Ser-6, Val-7, Cys-8, Leu-11, Leu-17, Leu-18 and tentatively Met-27. The sequence of the intact cell form from AtT-20 cells matches the sequence of the cell-free form of bovine pituitary precursor beginning at Trp-27, as determined by recombinant DNA technology [Nakanishi, S., Inoue, A., Kita, T., Nakamura, M., Chang, A. C. Y., Cohen, S. N., and Numa, S. (1979) Nature (Lond.) 278, 423-427]. The sequence of the mouse pituitary mRNA-directed cell-free translation product also matches the bovine precursor beginning at Pro-2. The results suggest that both the mouse and bovine precursors possess a signal sequence of 26 amino acids which is cleaved in intact cells. CNBr cleavage of [35S]cysteine-labelled intact cell precursor gave rise to an N-terminal fragment of a size compatible with the presence of a methionyl residue at or near position 27.
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000096:biosynthesis / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D005260:Female; D006801:Humans; D051379:Mice; D010911:Pituitary Neoplasms / Q000378:metabolism; D010920:Placenta / Q000378:metabolism; D011061:Poly A / Q000235:genetics; D011247:Pregnancy; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000235:genetics*; D012313:RNA / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012156:Reticulocytes / Q000378:metabolism; D008083:beta-Lipotropin / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D011498:Protein Precursors; D012333:RNA, Messenger; D011061:Poly A; D012313:RNA; D000324:Adrenocorticotropic Hormone; D008083:beta-Lipotropin