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Neurophysin I
Identifiers
Aliases	Oxytocin Associated NeurophysinOxytocin-Associated Neurophysin
External IDs	GeneCards: [1]; OMA:- orthologs
Orthologs
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	n; a
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	Wikidata
View/Edit Human

Neurophysin I is a carrier protein with a size of 10 KDa and contains 90 to 97 amino acids. It is a cleavage product (formed by splitting of a compound molecule into a simpler one) of preprooxyphysin.^[1] It is a neurohypophysial hormone that is transported in vesicles with oxytocin, the other cleavage product, along axons, from magnocellular neurons of the hypothalamus to the posterior lobe of the pituitary. Although it is stored in neurosecretory granules with oxytocin and released with oxytocin, its biological action is unclear.

Function

Neurophysin I is the carrier protein for oxytocin. It is produced in the cell bodies of the paraventricular and supraoptic nuclei and transported to its site of release in the axon terminals of the posterior pituitary. Neurophysin I neurons are more prevalent in the paraventricular nuclei while Neurophysin II neurons are more prevalent in the supraoptic nuclei.^[2] Vasopressin, a hormone similar in structure to oxytocin, is analogously bound and transported by Neurophysin II. Both hormones are nine residues long, and share seven of these residues. Oxytocin possesses Ile-3 and Leu-8 whereas vasopressin possesses Phe-3 and Arg-8. Both Ile and Phe are hydrophobic amino acids and undergo analogous binding to neurophysins.

Structure

The amino acid sequence of Neurophysin I is:

NH₂ - Ala - Ala - Pro - Asp - Leu - Asp - Val - Arg - Lys - Cys - Leu - Pro - Cys - Gly - Pro - Gly - Gly - Lys - Gly - Arg - Cys - Phe - Gly - Pro - Asn - Ile - Cys - Cys - Ala - Glu - Glu - Leu - Gly - Cys - Phe - Val - Gly - Thr - Ala - Glu - Ala - Leu - Arg - Cys - Gln - Glu - Glu - Asn - Tyr - Leu - Pro - Ser - Pro - Cys - Gln - Ser - Gly - Gln - Lys - Ala - Cys - Gly - Ser - Gly - Gly - Arg - Cys - Ala - Val - Leu - Gly - Leu - Cys - Cys - Ser - Pro - Asp - Gly - Cys - His - Ala - Asp - Pro - Ala - Cys - Asp - Ala - Glu - Ala - Thr - Phe - Ser - Gln – Arg - OH

(Disulfide bridge: 10-54; 13-27; 21-44; 28-34; 61-73; 67-85; 74-79)

References

^ Rao VV, Löffler C, Battey J, Hansmann I (1992). "The human gene for oxytocin-neurophysin I (OXT) is physically mapped to chromosome 20p13 by in situ hybridization". Cytogenet. Cell Genet. 61 (4): 271–3. doi:10.1159/000133420. PMID 1486803.
^ Wilkins; Evans (1972). "Demonstration of neurophysin in the hypothalamo-neurohypophysial system of the normal and dehydrated rat by the use of cross-species reactive anti-neurophysins". Zeitschrift für Zellforschung und mikroskopische Anatomie. 131 (2): 149–170. doi:10.1007/BF00306924. PMID 5074132. S2CID 22393640.