Neurophysins

Fig. 3. Processing steps of rat and bovine prepro-vasopressin lea ding to the hormone vasopressin and its carrier protein, neurophysin (14). (a) Putative signal peptide (b) vasopressin (c) neurophysin (d) glycopeptide. CHO = carbohydrate.

The nature of the hormone—NP link is unclear. Although the binding is quite specific, it is sufficientiy weak, ie, binding constant 10 10 M (71), as to cast doubt upon a protective role. However, no compelling evidence for a biological function for the neurophysins, other than as hormone carriers, has been elucidated (59,72). 

Biosynthesis. CRE is derived from a precursor of 196 amino acids (84,85). This gene contains one copy of CRE, which is flanked by double basic amino acids. The amino acid sequence of the CRE precursor suggests that it may arise from proteins related to POMC and neurophysins (31). The CRE precursor contains a cAMP responsive element which aHows stimulation of mRNA synthesis when intraceHular levels of cAMP are increased (86). 

Balaram, P., Bothner-By, A. A., Breslow, E. Nuclear magnetic resonance smdies of interaction of peptides and hormones with bovine neurophysin. Biochemistry 1973, 12, 4695 704. 

M. Rholam and P. Nicolas, Conformational flexibility of neurophysin as investigated by local motions of fluorophores. Relationships with neurohypophyseal hormone binding,... 

S. F. Scarlata and C. A. Royer, Ligand-induced asymmetry as observed through fluorophore rotations and free energy couplings Application to neurophysin, Biochemistry 25, 4925 4929 (1986). 

Oxytocin (Pitocin, Syntocinon) is a cyclic 8-amino acid peptide that is synthesized in the paraventricular nucleus of the hypothalamus and transported within hypothalamic neurons (in association with neurophysin) to the posterior pituitary for storage. Its mechanism of action involves the direct stimulation of oxytocin receptors found on the myometrial cells. Oxytocin circulates unbound in the plasma, where it has a half-Ufe of approximately 15 minutes. It is primarily inactivated in the kidneys and liver. 

The gene for arginine vasopressin is that of a 166-residue precursor protein carrying a 19-residue signal sequence at the N terminus.84 This sequence is followed by that of vasopressin, then after a GKR linker by the 95-residue neurophysin II. Finally, after one additional arginine there is a 39-residue glycopeptide. Oxytocin originates in a parallel way from its own precursor.85... 

Well-conditioned RPC can separate proteins that differ in rather small structural elements. The vasopressin-related neurophysin II, a polypeptide of 95 residues, could be separated into two isoforms that differ from each other only by one residue, either lie or Val, at position 89. This was possible by RPC on C 8 or C 18 columns (250 x 4.6 or 150 x 4.6 mm, respectively) with rather shallow gradients (6% B in 30 min or 20% B in 60 min). The gradient components were (triethyl ammonium phosphate buffer, pH 3)/acetonitrile76). 

Fassina G, Zamai M, Brigham-Burke M et al. Recognition properties of antisense peptide to Arg-8-vasopressin/bovine neurophysin II biosynthetic precursor sequences. Biochemistry 1989 28 8811. 

Fassina G, Lebl M, Chaiken IM, Screening the recognition properties of peptide hormone sequence mutants by analytical high performance liquid affinity chromatography on immobilized neurophysin, Coll. Czech. Chem. Commun., 53 2627-2636, 1988. 

Balaram P, Bothner-By AA, Breslow E, Localization of tyrosine at the binding site of neurophysin II by negative nuclear overhouser effects, J. Am. Chem. Soc., 94 4017—4018, 1972b. 

Mathiasen JR, Larson ER, Ariano MA, Sladek CD (1996) Neurophysin expression is stimulated by dopamine Di agonist in dispersed hypothalamic cultures. Am J Physiol 270 R404-R412. 

Anti-diuretic hormone (arginine vasopressin) is a nine-amino-acid peptide secreted from the posterior pituitary. Within hypothalamic neurons, the hormone is packaged in secretory vesicles together with a carrier protein called neurophysin both are released upon secretion. 

Sofroniew MV, Weindl A, Schrell LF, Wetzstein R (1981) Immunohistochemistry of vasopressin, oxytocin and neurophysin in the hypothedamus and extrahypothalamic regions of the humtin and primate brain. Acta Histochem S24 79-95... 

Swanson LW, McKellar S (1979) Distribution of oxytocin-stained and neurophysin-sttiined fibers in the spinal-cord of the rat and monkey. J Comp Neurol 188 87-106 Sweeney MI, White TD, Sawynok J (1987) Involvement of adenosine in the spintd tmtinociceptive effects of morphine and noradrenaline. J Pharmacol Exp Ther 243 657-665 Szabo B (2008) Pharmacology of cannabinoid receptors. Biotrend Rev 2 1—13 Szabo C (2007) Hydrogen sulphide and its therapeutic potential. Nat Rev Drug Discov 6 917-935 Szeto HH (2003) Dynorphin and the hypothalamo-pituitary-adrenal axis during fetal development. Life Sci 73 749-758... 

Another test of the resolving power of this new technique is to compare such separations with those achieved with conventional procedures. Glasel (II) found that neurophysins I and II, which were derived in an apparoitly chromatographically pure form by isoelectric focusing, were... 

Many protein isolations also involve the use of organic solvents at one or more purification steps, and thus one can often use this solvent in HPLC to maximize the recovery of protein samples. For example, apolipoproteins can be solubilized in isopropanol without loss of activity. For this reason Hancock and Sparrow 20) made extensive use of this solvent in the separation of C-apolipoproteins by reversed-phase HPLC. Glasel (//) found that neurophysins had a high solubility in aqueous methanol and used this solvent mixture in HPLC studies. 

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