Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Neurophysins”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources
PubMed1976

The hypothalamic-neurohypophysial system of the rat: localization and quantitation of neurophysin by light microscopic immunocytochemistry in normal rats and in Brattleboro rats deficient in vasopressin and a neurophysin.

The cellular distribution of neurophysin was examined in hypothalami and neural lobes of normal Long-Evans rats and Brattleboro rats deficient in vasopressin and a major neurophysin. Tissue sections were treated with antisera to bovine, human, and rat neurophysins, using immunoperoxidase bridge techniques. Antisera to oxytocin (OT) and vasopressin (VP) were applied to adjacent sections. Two distinct cell populations were discernible in both magnocellular nuclei on the basis of the intensity of cytoplasmic staining. About half of the magnocellular neurons in the supraoptic (SON) and paraventricular (PVN) nuclei of homozygous Brattleboro rats with diabetes insipidus (DI) were devoid of immunoreactive neurophysin, OT, and VP. These cells were presumably the defective counterparts of those neurons that produce VP and its associated neurophysin in normal and heterozygous Brattleboro rats. The cells in homozygous DI rats which were stained with immunoreaction products to NP and OT were more concentrated in the dorsal part of the SON and in the periphery of the PVN. Spatial segregation of different neurons was also seen in the neural lobe, where clusters of stained axons were surrounded by bundles of nerve fibers lacking immunoreactive material. In normal rats and heterozygotes nearly all magnocellular neurons reacted immunologically with antiserum to neurophysin but with different intensities, so that "dark" and "light" cells could be distinguished. The darker cells in heterozygous Brattleboro rats had the same pattern of distribution as cells which contained OT. In homozygous DI rats, only some of those cells which contained neurophysin and OT exhibited a positive reaction with antiserum to VP due to slight reactivity with OT. The results obtained in the homozygous Brattleboro rat would suggest that OT and VP and their associated neurophysins are produced in different neurons in both the SON and PVN. However, in normal rats and in heterozygous Brattleboro rats, VP appeared to be present in both OT-positive and OT-negative neurons suggesting that some cells may have the capacity to synthesize two hormones.

Animals↗
PubMed1976

Characterization of porcine neurophysin. III. Its resemblance and possible relationship to porcine neurophysin I.

Homogeneous porcine neurophysin III has been obtained from slightly contaminated neurophysin material by rechromatography on diethylaminoethyl-cellulose. The purified protein binds both oxytocin and lysine vasopressin. Gel filtration on a calibrated column of Sephadex G-75 gives an estimate of the molecular weight of 10,000. Amino acid analyses establish the composition Lyla8, 1/2Cys14, Val2, Met1, Ile2, Leu7, Tyr1, Phe3. The total number of amino acid residues is 95. This composition exceeds that of porcine neurophysin-I by 1 alanine and 2 arginine residues. It has an NH2-terminal alanine and the COOH-terminal sequence- Arg-Arg-Ala. Results of peptide maps, the amino acid composition of tryptic peptides, and the sequences of two small tryptic peptides suggest that porcine neurophysin III contains the entire molecule of porcine neurophysin I plus a tripeptide -Arg-Arg-Ala connected the COOH terminus. It is threfore possible that porcine neurophysin I may have been derived from porcine neurophysin III by the proteolytic removal of the last 3 or 4 amino acid residues from the COOH terminus, and that the porcine hypothalamic tissue synthesizes only two neurophysins, II and III.

Amino Acid Sequence↗
PubMed1981

Interaction of bromophenol blue and related dyes with bovine neurophysin-I: use as a probe of neurophysin chemistry.

The interaction of bromophenol blue and related dyes with bovine neurophysin-I was studied by equilibrium dialysis and gel filtration, absorption and circular dichroism spectroscopy, and analytical ultracentrifugation. Binding isotherms for bromophenol blue showed positive cooperativity, with one strong site and one or more weaker sites present per polypeptide chain at pH 4 and an apparent increase in relative importance of the weaker sites of lower pH. Circular dichroism (CD) studies suggested displacement of bound dye by peptides that bind to the neurophysin hormone binding site. Titration of bound bromophenol blue indicated that the deprotonated dye was bound to the strong site with approximately 20-fold greater affinity than the protonated dye. The pH dependence of binding of bromophenol blue and of bromocresol purple, which has a higher pKa than bromophenol blue, indicated that binding was dependent on protonation of a protein residue with a pKa of 2.9. This residue was identified as a protein carboxyl, probably on an abnormal side chain, by studies of glycine ethyl ester modified neurophysin and carboxypeptidase-treated neurophysin. The presence of exciton interactions between bound dye molecules when only one dye was bound per polypeptide chain and analytical ultracentrifugation results indicated that dye was bound predominantly to the dimeric form of the protein. The implication of the data are discussed with respect to a kinetic model of dye-neurophysin interaction, used elsewhere in a study of neurophysin dimerization, that assumed interaction of protein monomers with protonated dye. Additionally, results are presented which suggest, in disagreement with conclusions based on the kinetic model, that there is a pH-dependent component of neurophysin dimerization which parallels low pH fluorescence and CD changes observed earlier.

Animals↗
PubMed1976

Identification, in the external region of the rat median eminence, of separate neurophysin-vasopressin and neurophysin-oxytocin containing nerve fibres.

Immuno-enzyme cytochemical investigations, using single and double staining techniques, showed that the external region of the rat median eminence contains separate neurophysin-vasopressin fibres and neurophysin-oxytocin fibres. These neurophysin-hormone containing nerve fibres are influenced by bilateral adrenalectomy and by colchicine treatment. The external region of the median eminence of the homozygous Brattleboro rat contains neurophysin-oxytocin fibres. It does not contain immuno-reactive neurophysin-vasopressin fibres. Bilateral adrenalectomy also influences the neurophysin-vasopressin containing neurons of the suprachiasmatic nuclei. In the neurons of the parvicellular part of the rat hypothalamic paraventricular nuclei, staining for vasopressin and for oxytocin is completely absent.

Adrenalectomy↗
PubMed1987

Complete amino acid sequence of a VLDV-type neurophysin from ostrich differs markedly from known mammalian neurophysins.

The neurohypophyseal hormones vasopressin and oxytocin are known to be synthesized in eutherian mammals as part of larger precursors containing either MSEL- or VLDV-neurophysins. A neurophysin has been isolated from ostrich neurohypophyses and shown by partial amino acid sequence determination to be related to mammalian VLDV-neurophysin. The present report describes the complete amino acid sequence of this ostrich neurophysin containing 93 residues. This amino acid sequence, the first reported in birds, differs in a remarkable manner from its mammalian homolog. Indeed, it contains a large number of substitutions, including one insertion, distributed throughout the polypeptide chain when compared to known VLDV-neurophysins. Whereas many of these substitutions are localized inside the so-called constant region of the neurophysin, the highest variation can be found in the COOH-terminal region.

Amino Acid Sequence↗
PubMed1972

Evolution of neurophysin proteins: the partial sequence of bovine neurophysin-I (vasopressin-oxytocin-carrier proteins-automated amino-acid-sequence analysis-homology-protein evolution).

The sequence of the first 50 amino-acid residues of bovine neurophysin-I was determined. A comparison of this sequence with that of the 97-residue bovine neurophysin-II and the 92-residue porcine neurophysin-I molecules reveals a high degree of homology among these proteins. It is suggested that the binding site of neurophysin proteins for neurohypophyseal hormones is located in the middle portion of these molecules, where their sequences are virtually identical. The sequence data, as well as the occurrence of at least two neurophysins in both the pig and the cow, suggest that each species inherited at least two structural genes controlling the synthesis of these proteins. The most striking finding in the study was the observation of internal sequence homologies within the neurophysins. This result implies that these molecules arose by way of a series of partial gene duplications of a primitive gene that coded for a smaller ancestral protein.

Acetamides↗
PubMed1990

Development of neurophysin-containing neurons in primary cultures of rat hypothalami is related to the age of the embryo: morphological study and comparison of in vivo and in vitro neurophysins, oxytocin, and vasopressin content.

The morphological development of immunocytochemically identified neurophysin neurons and the evolution of neuropeptide content (neurophysins, vasopressin, and oxytocin) were studied in primary cultures of hypothalami obtained from 15- to 19-day-old embryos. According to their perikaryal surface, two populations of neurons were distinguished: large and small cells. Full development (defined by the perikaryal surface) of these neurons was reached at day 21 only in cultures from 15- or 16-day-old embryos. These two types of neurons may correspond to the magnocellular and parvocellular neurons described in vivo. Total neurophysins, vasopressin, and oxytocin content were measured by specific radioimmunoassays. Ontogeny of neurophysins and vasopressin showed a good correlation between cells cultured from 15- to 16-day-old embryos and hypothalami from age-matched rats. However, oxytocin was never detected in any of the cultures whatever the age of the embryos. Under our experimental conditions, hypothalamic primary cultures from 15- to 16-day-old embryos therefore appeared to be suitable for studying the differentiation and regulation of neurophysin- and vasopressin-containing neurons.

Animals↗
PubMed1991

Binding and fluorescence studies of the relationship between neurophysin-peptide interaction and neurophysin self-association: an allosteric system exhibiting minimal cooperativity.

The mechanism of peptide-enhanced neurophysin self-association was investigated to address questions raised by the crystal structure of a neurophysin-dipeptide complex. The dependence on protein concentration of the binding of a broad range of peptides to the principal hormone-binding site confirmed that occupancy of this site alone, and not a site that bridges the monomer-monomer interface, is the trigger for enhanced dimerization. For the binding of most peptides to the principal hormone-binding site on bovine neurophysin I, the affinity of each dimer site was at least 10 times that of monomer under the conditions used. No interactions between the two sites of the dimer were evident. Fluorescence polarization studies of pressure-induced dimer dissociation indicated that the volume change for this reaction was almost 4 times greater in the liganded than in the unliganded state, pointing to a significant alteration of the monomer-monomer interface upon peptide binding. Novel conformational changes in the vicinity of the single neurophysin tyrosine, Tyr-49, induced by pressures lower than required for subunit dissociation, were also observed. The bovine neurophysin I dimer therefore appears to represent an allosteric system in which there is thermodynamic and functional communication between each binding site and the monomer-monomer interface, but no communication across the interface to the binding site of the other subunit. A model for the peptide-enhanced dimerization is proposed in which intersubunit contacts between monomers reduce the large unfavorable free energy associated with binding-induced intrasubunit conformational change. Structural origins of the lack of communication across the interface are suggested on the basis of the low volume change associated with dimerization in the unliganded state and monomer-monomer contacts in the crystal structure. Potential roles for the peptide alpha-amino group and position 2 phenyl ring in triggering conformational change are discussed.

Allosteric Regulation↗
PubMed1987

Application of peptide-mediated ring current shifts to the study of neurophysin-peptide interactions: a partial model of the neurophysin-peptide complex.

Perdeuteriated peptides were synthesized that are capable of binding to the hormone binding site of neurophysin but that differ in the position of aromatic residues. The binding of these peptides to bovine neurophysin I and its des-1-8 derivative was studied by proton nuclear magnetic resonance spectroscopy in order to identify protein residues near the binding site through the observation of differential ring current effects on assignable protein resonances. Phenylalanine in position 3 of bound peptides was shown to induce significant ring current shifts in several resonances assignable to the 1-8 sequence, including those of Leu-3 and/or Leu-5, but was without effect on Tyr-49 ring protons. The magnitude of these shifts was dependent on the identity of peptide residue 1. By contrast, the sole demonstrable direct effect of an aromatic residue in position 1 was a downfield shift in Tyr-49 ring protons. Study of peptide binding to des-1-8-neurophysin demonstrated similar conformations of native and des-1-8 complexes except for the environment of Tyr-49, confirmed the peptide-induced ring current shift assignments in native neurophysin, and indicated an effect of binding on Thr-9. These observations are integrated with other results to provide a partial model of neurophysin-peptide complexes that places the ring of Tyr-49 at a distance 5-10 A from residue 1 of bound peptide and that places both the 1-8 sequence and the protein backbone region containing Tyr-49 proximal to each other and to peptide residue 3.(ABSTRACT TRUNCATED AT 250 WORDS)

Indicators and Reagents↗
PubMed2002

NMR analysis of the monomeric form of a mutant unliganded bovine neurophysin: comparison with the crystal structure of a neurophysin dimer.

Determination of the structure of the unliganded monomeric state of neurophysin is central to an understanding of the allosteric relationship between neurophysin peptide-binding and dimerization. We examined this state by NMR, using the weakly dimerizing H80E mutant of bovine neurophysin-I. The derived structure, to which more than one conformer appeared to contribute, was compared with the crystal structure of the unliganded des 1-6 bovine neurophysin-II dimer. Significant conformational differences between the two proteins were evident in the orientation of the 3,10 helix, in the 50-58 loop, in beta-turns, and in specific intrachain contacts between amino- and carboxyl domains. However, both had similar secondary structures, in independent confirmation of earlier circular dichroism studies. Previously suggested interactions between the amino terminus and the 50-58 loop in the monomer were also confirmed. Comparison of the observed differences between the two proteins with demonstrated effects of dimerization on the NMR spectrum of bovine neurophysin-I, and preliminary investigation of the effects of dimerization on H80E spectra, allowed tentative distinction between the contributions of sequence and self-association differences to the difference in conformation. Regions altered by dimerization encompass most binding site residues, providing a potential explanation of differences in binding affinity between the unliganded monomeric and dimeric states. Differences between monomer and dimer states in turns, interdomain contacts, and within the interdomain segment of the 50-58 loop suggest that the effects of dimerization on intrasubunit conformation reflect the need to adjust the relative positions of the interface segments of the two domains for optimal interaction with the adjacent subunit and/or reflect the dual role of some residues as participants both at the interface and in interdomain contacts.

Allosteric Regulation↗
PubMed1996

Thermodynamic role of the pro region of the neurophysin precursor in neurophysin folding: evidence from the effects of ligand peptides on folding.

Attention has focused recently on the role of amino-terminal precursor pro regions in protein folding, with particular emphasis on their effects on folding kinetics. We examined the kinetic and thermodynamic effects of ligand peptides on the folding of neurophysin from the reduced state; these peptides serve as analogs of the pro regions of the common precursors of the neurophysins and the hormones oxytocin and vasopressin. Folding of reduced, mononitrated bovine neurophysin-II was monitored by circular dichroism in a glutathione redox buffer. The results confirmed the ability of neurophysin to fold to a limited extent (20-25% in this system) in the absence of ligand peptides. Ligand peptides increased the efficiency of folding to 100%, the exact efficiency being dependent on peptide identity and concentration. However, the rate of folding was peptide-independent. Analysis of the folding reaction demonstrated relatively rapid conversion of the reduced state to a disulfide-scrambled state, which slowly converted (half-life of 5 h at pH 7.3) to the folded state. Native unliganded neurophysin also equilibrated with the disulfide-scrambled state in the same redox buffers. For each peptide, an equilibrium constant for the folding reaction, representing the amount of peptide bound in the folding system as a function of peptide concentration, was calculated. Comparison of this constant with the intrinsic binding constants of the native protein allowed the derivation, under conditions at or approaching thermodynamic reversibility, of the relative stability of the native and disulfide-scrambled states. The results indicate that the scrambled state, which probably represents the presence of incorrect disulfide pairs in both protein domains, is more stable than the native unliganded state by approximately 1 kcal/mol in this system. The role of ligand peptide therefore is to stabilize the folded protein after it is formed, i.e., it provides a thermodynamic sink. The results contrast with the putative behavior of exogenous peptides representative of the pro regions of subtilisin and alpha-lytic protease, which are generally considered to facilitate folding by reaction with folding intermediates. A potential alternative view of the role of propeptides in protease folding is suggested.

Animals↗
PubMed1989

Influence of neurophysin residues 1-8 on the optical activity of neurophysin-peptide complexes. Direct evidence that the 1-8 sequence alters the environment of bound peptide.

Circular dichroism was used to compare the environment of peptides bound to native and des 1-8 neurophysin in order to further elucidate the role of the neurophysin 1-8 sequence in peptide-binding. A very large positive ellipticity (approximately 6000 deg cm2 dmol-1), shown earlier to be induced in tyrosine at position 2 of peptides bound to the native protein, was determined by the present study to be paralleled by similar induced changes in tyrosine at peptide position 1. Deletion of the neurophysin 1-8 sequence led to loss of half of the induced optical activity at peptide positions 1 and 2 and changes in binding-induced optical activity in the protein, the latter partially assignable to protein disulfides. In the mononitrated native and des 1-8 proteins, the optical activity of neurophysin Tyr-49, a residue at the peptide-binding site, was reduced by 80% in complexes of the des 1-8 protein relative to those of the native protein. The results suggest a role for neurophysin Arg-8 in modulating the optical activity at the binding site by directly placing a charge proximal to the binding site and/or by altering binding site conformation. The data provide the first unambiguous evidence of a difference in the environment of bound peptide between the native and des 1-8 proteins.

Binding Sites↗
PubMed1980

Magnocellular hypothalamic projections to the lower brain stem and spinal cord of the rat. Immunocytochemical evidence for predominance of the oxytocin-neurophysin system compared to the vasopressin-neurophysin system.

The paraventricular nucleus of the rat hypothalamus has been shown to project to the medulla and spinal cord. The proportion of oxytocin-neurophysin (OTNP) axons to vasopressin-neurophysin (VPNP) axons in these structures is unknown. A major difficulty in resolving this problem in previous immunocytochemical studies was the lack of a specific antiserum to each rat neurophysin. In this study two approaches have been used: (1) comparison of immunostaining for neurophysin in normal versus homozygous Brattleboro rats with diabetes insipidus (HODI) which lack VPNP, and (2) application of an antiserum to both rat neurophysins absorbed with HODI rat hypothalamic-pituitary extracts which contain only OTNP. The latter would result in an antiserum specific for VPNP. Our results indicate that the axons which constitute the caudal projections from the paraventricular nucleus are predominately oxytocinergic, the vasopressinergic innervation being limited to the nucleus tractus solitarius, the dorsal motor nucleus of vagus, and the substantia gelatinosa. A similar number of reactive fibers were seen in the medulla and spinal cord of normal and HODI rats. No positive perikarya were observed caudal to the hypothalamus. Fibers in the medulla appeared to terminate in the nucleus of the solitary tract and in the dorsal motor nucleus of the vagus nerve. Positive fibers throughout the cord were present in the substantia gelatinosa and in the intermediolateral grey. The possible role(s) of these projections in integrating autonomic functions and afferent information with neuroendocrine regulation is discussed.

Animals↗
PubMed1975

Identification of separate vasopressin-neurophysin II and oxytocin-neurophysin I containing nerve fibres in the external region of the bovine median eminence.

Immuno-enzyme histochemical investigations showed the presence, in the external region of the bovine median eminence, of accumulations of vasopressin-neurophysin II- and oxytocin-neurophysin I-complexes. These two hormone-neurophysin complexes are located in separate fine varicose nerve fibres. The results strongly plead against an important role of tanycytes in the transport of vasopressin, oxytocin and neurophysins from the cerebrospinal fluid to the hypophysial portal blood-vessels.

Animals↗
PubMed1991

The hormone-binding site of neurophysins: binding of vasopressin to the N-terminal sub-domain dissected from human MSEL-neurophysin through endopeptidase Lys-C.

Human MSEL-neurophysin has been dissected into two halves by endopeptidase Lys-C, taking advantage of a peculiar Lys59-Ala60 bond. Two sub-domains, N-terminal (1-59) and C-terminal (60-93), have been separated. These sub-domains have been purified by reverse-phase high pressure liquid chromatography and identified by their N-terminal sequences. The N-terminal fragment comprises two chains 1-18 and 19-59, because of the presence of a second lysine residue in position 18, whereas the C-terminal fragment (60-93) is a single chain. Hormone-binding experiments have been carried out using vasopressin or vasopressinyl-Gly-Lys-Arg and testing the ability of the hormone-neurophysin complex to precipitate at pH 3.9 with 10% NaCl. The N-terminal sub-domain precipitates in presence of vasopressin in the same way as native neurophysin whereas the C-terminal sub-domain does not. It can be concluded that the hormone-binding site is located in the 1-59 region of neurophysin.

Amino Acid Sequence↗
PubMed1986

Analytical high-performance affinity chromatography: evaluation by studies of neurophysin self-association and neurophysin-peptide hormone interaction using glass matrices.

Bovine neurophysin II (BNP II) was covalently immobilized on both nonporous and porous (200-nm pore diameter) glass beads and incorporated in a high-performance liquid chromatograph to evaluate analytical high-performance affinity chromatography as a microscale method for characterizing biomolecular interactions. By extension of the theoretical treatment of analytical affinity chromatography, both the self-association of neurophysin and its binding of the peptide hormone vasopressin were characterized by using a single chromatographic column containing immobilized neurophysin predominantly in the monomer form. Both [3H] [Arg8]vasopressin (AVP) and 125I-BNP II were rapidly eluted (less than 25 min). The relatively symmetrical elution peaks obtained allowed calculation of both equilibrium dissociation constants and kinetic dissociation rate constants. The dissociation constant measured chromatographically for the AVP-immobilized neurophysin complex, KM/L = 11 microM with porous glass beads and 75 microM with nonporous glass (NPG) beads, was in reasonable agreement with those previously obtained by curve fitting of Scatchard plots (16-20 microM) and from binding to [BNP II]Sepharose (50 microM). The values obtained are larger than that for dissociation of AVP from BNP II dimer, by a factor consistent with the intended nature of immobilized BNP II as monomers. Chromatography of BNP II on the [BNP II]NPG gave a dimer dissociation constant of 166 microM, a value in excellent agreement with that derived from equilibrium sedimentation studies (172 microM). In contrast to the agreement of chromatographic equilibrium binding constants with those measured in solution, the dissociation rate, k-3, determined from the variance of the affinity chromatographic elution profile with nonporous beads, was several orders of magnitude smaller than the solution counterpart.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1966

The preparation and properties of porcine neurophysin and the influence of calcium on the hormone-neurophysin complex.

1. The preparation of a hormone-binding protein fraction (neurophysin) from porcine neurohypophyses is described.2. It was shown by gel-filtration that the protein (which sedimented as a single component on analytical ultracentrifugation) forms complexes with oxytocin and lysine vasopressin. The maximum capacity of porcine neurophysin to bind oxytocin and lysine vasopressin was estimated from the results of dialysis experiments as 232 u. oxytocin and 48 u. lysine vasopressin/mg protein.3. Binding of oxytocin and lysine vasopressin by neurophysin was completely inhibited in the presence of calcium in concentrations greater than 10(-6)M but is unaffected at less than 10(-7)M-Ca. The concentration of calcium required to inhibit binding did not appear to be dependent on hormone or protein concentrations.4. No evidence was obtained that calcium was bound by neurophysin or by the peptide hormones either alone or in combination.5. These results are discussed in the light of the hypothesis that release of the hormone from the neurohypophysis is mediated by calcium.

Animals↗