Neurophysins are carrier proteins for the hormones generated in the hypothalamus and distributed from the posterior pituitary.Neurophysin II is a carrier protein which binds vasopressin. It is generated from the same precursor as vasopressin.It can be associated with neurohypophyseal diabetes insipidus.Neurophysin II is also known as a stimulator of Prolactin secretion. Neurophysin II (NPII) is a 10-kDa, Vasopressin (VP)-binding peptide that is a proteolytically generated product of the Arginine-Vasopressin gene (AVP). This gene codes for a common precursor that contains the peptide sequences for VP (9 aa) and NPII (95 aa). NPII is a two beta-sheet domain peptide that contains 7 disulfide bonds. Intracellularly, it binds VP, protecting it from proteolysis and promoting proper precursor cleavage. When bound to VP, NPII forms a heterotetrameric complex [(NPII/VP)2].