Trypsin liberates an arginine vasopressin-like peptide and neurophysin from a Mr 20,000 putative common precursor.
Although the hypothesis that vasopressin and its associated neurophysin are synthesized together in one macromolecular common precursor was put forward more than a decade ago, direct conformation of this hypothesis has been lacking. A [35S]cysteine-labeled putative precursor for vasopressin-related neurophysin (Mr 20,000, pI 6.1) has been isolated from the supraoptic nuclei of rats. This precursor was subjected to limited proteolysis with trypsin which produced a Mr 10,000 protein and peptide products. The former was identified as neurophysin on the basis of its pH-dependent affinity for vasopressin and its behavior in isoelectric focusing systems (pI 4.6-4.8). The tryptic peptides proved to be vasopressin-like because they: (i) were rich in cysteine, (ii) comigrated with vasopressin on gel filtration columns in 6 M guanidine HCl, (iii) bound to a neurophysin-Sepharose affinity column at pH 5.7, and (iv) were recognized by antibodies against vasopressin. These data on the Mr 20,000, pI 6.1 protein represent direct experimental evidence for a candidate for the common precursor of vasopressin and neurophysin. We propose that this common precursor be called "propressophysin."
D000818:Animals; D001127:Arginine Vasopressin / Q000096:biosynthesis*; D002845:Chromatography / Q000379:methods; D005260:Female; D008970:Molecular Weight; D009481:Neurophysins / Q000096:biosynthesis*; D010446:Peptide Fragments / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism*; D051381:Rats; D013495:Supraoptic Nucleus / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism*
D009481:Neurophysins; D010446:Peptide Fragments; D011498:Protein Precursors; D001127:Arginine Vasopressin; D014357:Trypsin