title: Biosynthetic fate of the amino-terminal fragment of pro-opiomelanocortin within the intermediate lobe of the mouse pituitary.
abstract: All the biosynthetic derivatives of pro-opiomelanocortin (POMC) were purified from an extract of 300 mouse neurointermediate pituitaries. Inspection of the amino acid composition of these peptides indicated that cleavage at all available dibasic processing sites within POMC was essentially complete except for -Arg49-Lys50- within the 1 to 74 amino-terminal sequence. Only about 50% of the 1 to 74 fragment was processed to the 1 to 49 sequence and Lys1 gamma 3MSH (i.e., the 50 to 74 sequence). The existence of these derivatives of the 1 to 74 fragment was confirmed by pulse-labelling explant cultures of mouse neurointermediate pituitaries with tritiated amino acids. Pulse/chase biosynthetic experiments indicated that the cleavage of the 1 to 74 sequence takes place 3 to 6 hours post-translation. This time course of biosynthesis suggests that the cleavage of the 1 to 74 sequence is a secretory granule event. Time course studies revealed that the minimum time required for newly synthesized derivatives of POMC to emerge from the intermediate lobe tissue was approximately 3 hours.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001120:Arginine / Q000378:metabolism; D003470:Culture Media; D007930:Leucine / Q000378:metabolism; D008358:Mannose / Q000378:metabolism; D051379:Mice; D009924:Organ Culture Techniques; D010446:Peptide Fragments / Q000096:biosynthesis*; D010904:Pituitary Gland, Posterior / Q000378:metabolism*; D011333:Pro-Opiomelanocortin / Q000096:biosynthesis*; D013431:Sulfates / Q000378:metabolism; D013462:Sulfur Radioisotopes; D014316:Tritium
chemical_list: D000596:Amino Acids; D003470:Culture Media; D010446:Peptide Fragments; D013431:Sulfates; D013462:Sulfur Radioisotopes; C031562:pro-opiomelanocortin amino-terminal glycopeptide; D014316:Tritium; D011333:Pro-Opiomelanocortin; D001120:Arginine; D007930:Leucine; D008358:Mannose