Deduced amino acid sequence from the bovine oxytocin–neurophysin I precursor cDNA

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Abstract
The nonapeptide hormone oxytocin-like arginine-vasopressin (AVP)1–4 is synthesized as part of a larger precursor polypeptide. The precursor also includes the neurophysin molecule with which the hormone is associated in the neurosecretory granules of the hypothalamo-pituitary tract. A protein of molecular weight (Mr) ∼ 20,000 has been isolated from supraoptic nuclei of rat hypothalami which, after tryptic cleavage, released a neurophysin-like molecule of Mr ∼ 10,000 and an oligopeptide related to oxytocin5. This result was complemented by in vitro translation of bovine hypothalamic mRNA6–8. Among the primary translation products a single polypeptide of Mr ∼ 16,500 was shown to contain antigenic determinants recognized by specific antisera against bovine neurophysin I and oxytocin. Here we report the amino acid sequence of the bovine oxytocin–neurophysin I (OT-NpI) precursor which was derived from sequence analysis of the cloned cDNA. As is the case for the bovine arginine-vasopressin–neurophysin II (AVP-NpII) precursor4, the signal sequence of the OT-NpI precursor is immediately followed by the nonapeptide hormone which is connected to neurophysin I by a Gly-Lys-Arg sequence. A striking feature of the nucleic acid sequence is the 197-nucleotide long perfect homology with the AVP-NpII precursor mRNA sequence encoding the conserved middle part of neurophysins I and II.

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