View source for Neurophysin II

{{Short description|Cleavage product of the arginine vasopressin gene}}
{{More references needed|date=January 2024}}
{{protein
|Name=arginine vasopressin (neurophysin II, antidiuretic hormone, diabetes insipidus, neurohypophyseal)
|caption= neurophysin II, Bos taurus
|image= 2bn2.jpg
|width= 270
|HGNCid=894
|Symbol=AVP
|AltSymbols=ARVP
|EntrezGene=551
|OMIM=192340
|RefSeq=NM_000490
|UniProt=P01185
|PDB=
|ECnumber=
|Chromosome=20
|Arm=p
|Band=13
|LocusSupplementaryData=
}}

'''Neurophysin II''' is a [[carrier protein]] with a size of 19,687.3 [[Atomic mass unit|Da]] and is made up of a [[Protein dimer|dimer]] of two virtually identical chains of [[amino acid]]s. Neurophysin II is a cleavage product (formed by splitting of a compound molecule into a simpler one) of the [[AVP gene|''AVP'' gene]]. It is a neurohypophysial [[hormone]] that is transported in vesicles with [[vasopressin]], the other cleavage product, along [[axon]]s, from magnocellular neurons of the [[hypothalamus]] to the posterior lobe of the [[pituitary]]. Although it is stored in neurosecretory granules with vasopressin and released with vasopressin into the bloodstream, its biological action is unclear. Neurophysin II is also known as a stimulator of [[prolactin]] secretion.

== Function ==
Neurophysin II is a carrier protein for vasopressin (ADH). 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. [[Oxytocin]], a hormone similar in structure to vasopressin, is analogously bound and transported by [[neurophysin I]]. Both hormones are nine residues long, and only differ by the amino acids at positions three and eight. Oxytocin possesses Ile-3 whereas vasopressin possesses Phe-3. Both Ile and Phe are hydrophobic amino acids and undergo analogous binding to neurophysins.

== Structure ==
Neurophysin II is a dimer with each monomer consisting of two anti-parallel β-sheets. Each chain is identical with the exception of a single amino acid substitution (Chain 1 contains Lys-18, whereas chain 2 contains Ala-18). Each chain is 95 amino acids in length and binds a single oxytocin molecule.
The amino acid sequence of Neurophysin II is:

NH<sub>2</sub> - Ala - Met - Ser - Asp - Leu - Glu - Leu - Arg - Gln - Cys - Leu - Pro - Cys - Gly - Pro - Gly - Gly - Lys - Gly - Arg - Cys - Phe - Gly - Pro - Ser - Ile - Cys - Cys - Ala - Asp - 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 - Ala - Phe - Gly - Val - Cys - Cys - Asn - Asp - Glu - Ser - Cys - Val - Thr - Glu - Pro - Glu - Cys - Arg - Glu - Gly - Phe - His - Arg - Arg - Ala - OH

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

== Clinical significance ==
Point mutations in the genes that encode arginine vasopressin and or its carrier protein neurophysin II underlie most cases of the familial, autosomal dominant disorder [[neurohypophyseal diabetes insipidus]]<ref name="pmid14673472">{{cite journal  |vauthors=Christensen JH, Siggaard C, Corydon TJ, etal |title=Six novel mutations in the arginine vasopressin gene in 15 kindreds with autosomal dominant familial neurohypophyseal diabetes insipidus give further insight into the pathogenesis |journal=Eur. J. Hum. Genet. |volume=12 |issue=1 |pages=44–51 |date=January 2004 |pmid=14673472 |doi=10.1038/sj.ejhg.5201086|doi-access=free }}</ref> (also called hereditary hypothalamic [[diabetes insipidus]]). This condition results from insufficient [[Vasopressin|ADH]] release into systemic circulation.

== See also ==
* [[Copeptin]]
* [[Neurophysins]]
* [[Neurophysin I]]

==References==
{{reflist}}

==External links==
* {{MeshName|Neurophysin+II}}

{{Carrier proteins}}
{{Oxytocin and vasopressin receptor modulators}}