Characterization of a common precursor to corticotropin and beta-lipotropin: identification of beta-lipotropin peptides and their arrangement relative to corticotropin in the precursor synthesized in a cell-free system.
Radioactive proteins synthesized in an mRNA-dependent reticulocyte cell-free system under the direction of mRNA from AtT-20/D-16v mouse cells were isolated by specific immunoprecipitation using antiserum to either alpha(1-24) corticotropin or beta-endorphin [beta(61-91) lipotropin]. Each immunoprecipitate was fractionated by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and shown to contain only one labeled protein with an apparent molecular weight of 28,500. Tryptic peptide analysis of the Mr 28,500 corticotropin and beta-lipotropin molecules isolated from the gels demonstrated that the two proteins had the same lysine, methionine, and tryptophan peptides. Four tryptic peptides from the cell-free product exhibited the same electrophoretic and chromatographic mobilities as marker tryptic peptides from bovine beta-melanotropin and porcine beta-endorphin. The identification of these peptides was confirmed by amino acid composition studies with a variety of labeled amino acids. The beta-lipotropin tryptic peptides were also shown to be located carboxy terminal to the corticotropin tryptic peptides.
D000324:Adrenocorticotropic Hormone / Q000096:biosynthesis*; D000595:Amino Acid Sequence; D002460:Cell Line; D002474:Cell-Free System; D006023:Glycoproteins / Q000096:biosynthesis; D008970:Molecular Weight; D010902:Pituitary Gland / Q000378:metabolism*; D011132:Polyribosomes / Q000378:metabolism; D011498:Protein Precursors / Q000096:biosynthesis*; D012156:Reticulocytes / Q000378:metabolism; D008083:beta-Lipotropin / Q000096:biosynthesis*
D006023:Glycoproteins; D011498:Protein Precursors; D000324:Adrenocorticotropic Hormone; D008083:beta-Lipotropin