title: Structure of a guinea pig common precursor to a MSEL-type neurophysin and copeptin.
abstract: From guinea pig posterior pituitaries, a MSEL-type neurophysin (neurophysin containing methionine-2, serine-3, glutamic acid-6 and leucine-7), a glycopeptide referred to as copeptin and their common precursor have been purified to homogeneity and sequenced. The performed acid-oxidized precursor, subjected to trypsin hydrolysis, has given 9 peptides, 6 of which (T1-T6) identical to those given by oxidized MSEL-neurophysin except that T6 has an additional C-terminal arginine residue when compared to its homologue. The other 3 tryptic peptides (T7-T9) are identical to those given by copeptin. The 132-residue precursor therefore comprises a MSEL-type neurophysin (93 residues) and copeptin (38 residues) linked by an arginine residue. The molar proportion of this bound form compared with the free polypeptides is approximately 20%. It is believed that this precursor is a part of the vasopressin-MSEL-neurophysin-copeptin precursor incompletely processed during the transport from hypothalamus to neurohypophysis.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001127:Arginine Vasopressin / Q000302:isolation & purification*; D006020:Glycopeptides / Q000302:isolation & purification*; D006168:Guinea Pigs; D008970:Molecular Weight; D009481:Neurophysins / Q000302:isolation & purification*; D010121:Oxytocin; D010446:Peptide Fragments / Q000302:isolation & purification; D010904:Pituitary Gland, Posterior / Q000032:analysis; D011498:Protein Precursors / Q000302:isolation & purification*
chemical_list: D006020:Glycopeptides; D009481:Neurophysins; D010446:Peptide Fragments; D011498:Protein Precursors; D001127:Arginine Vasopressin; D010121:Oxytocin