Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The character of temperature dependence of hydrolytic and transport functions of Na, K-ATPase is analyzed. It is shown that the nonlinear Arrhenius plot is typical only of "allosteric" substrates ATP and CTP, the inflection of curves reflecting sensitivity of the enzyme to the phase reconstructions of membrane lipids. The linear Arrhenius plots are typical of GTP, UTP- p-NPP and acetyl phosphate, the substrates demonstrating "normal" kinetics of Michaelis and not providing the active transport of ions. A conclusion is drawn that anomalies on the Na, K-ATPase temperature dependence evidence for the lipid control of intersubunit interactions in the supermolecular complex of Na, K-ATPase which are realized during the active transport of ions.
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PMID:[Characteristics of temperature dependence of Na,K-ATPase]. 284 87

Binding of beta-melanotropin (beta-MSH) and subsequent activation of adenylate cyclase in the M2R mouse melanoma cell line is strongly dependent on the concentration of extracellular free calcium. This effect can be demonstrated both in the intact cell and in a plasma membrane preparation derived therefrom, using an EGTA buffer system. In contrast, stimulation of adenylate cyclase by prostaglandin E1, forskolin, or guanosine 5'-O-(2-thiotriphosphate) is calcium insensitive. It is shown that calcium increases the binding affinity of beta-MSH for its receptor by a factor of 20 (from 400 nM to 20 nM) without affecting maximal hormone binding. At supersaturating concentrations of beta-MSH (greater than 200 nM) binding gradually becomes calcium independent. Hormone-receptor complexes formed in the presence of calcium dissociated rapidly (less than or equal to 2 min) and reversibly upon the elimination of calcium by excess EGTA. Among nine divalent metal cations tested, calcium was found to be the most effective in facilitating hormone binding. Whereas calcium promotes beta-MSH binding, GTP and its stable analogs lead to a reduction in both maximal binding (65%) and affinity (2-fold). These effects are calcium independent, suggesting that the reciprocal control of beta-MSH binding by calcium and guanosine nucleotides is mediated by two separate and independent mechanisms.
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PMID:Dual regulation of beta-melanotropin receptor function and adenylate cyclase by calcium and guanosine nucleotides in the M2R melanoma cell line. 302 27

Possible coupling of bovine adrenal medullary opioid receptors to islet-activating protein (IAP, pertussis toxin)-sensitive GTP-binding proteins was investigated by studying effects of guanyl-5'-yl imidodiphosphate (Gpp(NH)p) and IAP treatment of membranes on opioid binding. Gpp(NH)p inhibited [3H]D-Ala2-D-Leu5-enkephalin ([3H]DADLE) binding by increasing the dissociation constant of [3H]DADLE and membranes, and enhanced slightly [3H]diprenorphine binding. IAP treatment of membranes reduced [3H]DADLE binding and abolished almost completely the Gpp(NH)p inhibition of [3H]DADLE binding. Treatment of membranes with IAP and [32P]NAD resulted in radio-labeling of membrane proteins of approximately 39,000 dalton. DADLE inhibited adenylate cyclase activity in rat brain caudate nucleus. However, DADLE, beta-endorphin, levorphanol and dynorphin A(1-13) did not show any significant inhibitory action on bovine adrenal medullary adenylate cyclase activity. These results suggest that bovine adrenal medullary opioid (DADLE) receptors are linked to IAP-sensitive GTP-binding proteins which are not directly coupled to adenylate cyclase.
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PMID:Coupling of adrenal medullary opioid receptors to islet-activating protein-sensitive GTP-binding proteins. 303 14

In this study, two melanotropin binding proteins from M2R melanoma cells have been identified based on the photochemical cross-linking of [125I]iodinated porcine beta-MSH ([ 125I]iodo-beta-MSH) to melanoma cell membranes, using N-hydroxysuccinimidyl-azidobenzoate. Autoradiography of photoaffinity-labeled M2R membrane protein, after sodium dodecyl sulfate-polyacrylamide gel electrophoresis, revealed the specific labeling of two separate bands with an apparent molecular mass of 43 and 46 kilodaltons, respectively. Photoaffinity labeling of both bands was of near-equal intensity and could be inhibited, in a dose-dependent manner, by the addition of unlabeled beta-MSH before photolysis. In addition, agents known to inhibit the binding of beta-MSH to its cellular receptor, such as EGTA, GTP, guanosine 5'-O-(3-thio)triphosphate, and a synthetic analog of the calmodulin-binding domain of myosin light chain kinase-M5, were all found to specifically inhibit the labeling of these two protein bands by the azido derivative of [125I]iodo-beta-MSH. In contrast, addition of a nonrelated peptide, vasoactive intestinal peptide, had no effect upon the labeling of these melanotropin-binding proteins. On the basis of these results we suggest that the two proteins may function as the binding domain(s) of the cellular receptor for melanotropins, or may represent entire receptor moieties themselves.
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PMID:Identification and characterization of melanotropin binding proteins from M2R melanoma cells by covalent photoaffinity labeling. 341 15

The non-hydrolyzable GTP analogue, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) and cyclic AMP potentiated the Ca2+-evoked secretion of alpha-melanocyte-stimulating hormone (alpha-MSH) from permeabilized neurointermediate lobe (IL) cells of rat pituitary gland. The enhancement by Mg-GTP gamma S (100 microM) and cyclic AMP (1 microM) depended on the intracellular Ca2+ concentration (EC50 = 4.8 +/- 1.8 and 4.6 +/- 1.7 microM; mean +/- SE, with and without Mg-GTP gamma S and cyclic AMP, respectively). A similar effect was observed with guanine nucleotide triphosphate (GTP and GppNHp). Mg was absolutely required for this event. Neither Mg-GTP gamma S nor cyclic AMP alone was effective in potentiating alpha-MSH secretion. GDP beta S blocked the Mg-GTP gamma S (100 microM) and cyclic AMP augmented secretion of alpha-MSH. Neither neomycin (which affects the process of inositol 1,4,5-triphosphate-mediated Ca2+ mobilization) or colchicine (which influences microtubule assembly) had an effect on the cyclic AMP and Mg-GTP gamma S potentiation of alpha-MSH secretion. These data suggest that the GTP-binding protein may be involved in the regulation of alpha-MSH secretion after Ca2+ entry into the cells, since the intracellular environment is controlled in the permeabilized cells.
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PMID:Alpha-melanocyte-stimulating hormone secretion from permeabilized intermediate lobe cells of rat pituitary gland. The role of guanine nucleotides. 360 97

Two different classes of binding sites probably related to serotonergic receptors have already been reported: 5-HT1 binding sites recognize [3H]5-hydroxytryptamine with a high affinity (Kd = 3 nM) and S2 binding sites recognize [3H]spiroperidol and [3H]ketanserine. An additional population of sites has been observed in crude membrane preparations or fractions enriched with synaptosomal membranes obtained from rat brain cortex. This population was observed as a single class of sites in a synaptosomal fraction (L fraction--according to Laduron (1977)). It corresponded to a dissociation constant Kd = 13-15 nM, and Bmax = 0.80 +/- 0.15 pmol/mg protein. Displacement experiments showed that it recognized preferentially the 5-HT structure (bufotenin, 5-MeO-tryptamine). Tryptamine was a weak displacer and 5,7-dihydroxytryptamine totally inefficient. Neither 8-OH-DPAT, nor quipazine had any effect. Methiothepin, cinanserin and cyproheptadine displaced 5-HT from these sites whereas ergot derivatives did not. Contrary to 5-HT1 binding, this recently observed binding was not altered by GTP; alpha-MSH reduced the corresponding Bmax whereas Leu-enkephalin did not. The degenerative lesion of the serotonergic fibers led to a slight increase in the Bmax of the binding without altering the Kd which means that corresponding sites are not located on serotonergic fibers and might be postsynaptically located.
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PMID:Multiple high affinity binding sites for 5-hydroxytryptamine: a new class of sites distinct from 5-HT1 and S2. 405 78

The D-2 dopamine receptor mediates inhibition of adenylate cyclase in rat intermediate lobe; this receptor is linked to cyclase by the inhibitory guanyl nucleotide-binding protein (Ni). The functioning of components in the inhibitory system was compared in control and pertussis toxin-treated tissues. (-)-N-n-Propylnorapomorphine ((-)-NPA), a dopamine agonist, and 5'-guanylyl imidodiphosphate (Gpp(NH)p), a nonhydrolyzable GTP analog, caused a dose-dependent inhibition of adenylate cyclase in control tissue. Pertussis toxin abolished dopamine receptor-mediated inhibition of adenylate cyclase but did not alter Gpp(NH)p-induced inhibition of cyclase. In control tissue, GTP blocked Gpp(NH)p inhibition of cyclase in the absence, but not in the presence of (-)-NPA. Following pertussis toxin treatment, GTP blocked the inhibitory effect of Gpp(NH)p either in the absence or in the presence of (-)-NPA. Pertussis toxin did not alter the number of dopamine receptors or the affinity of the receptor for [3H]spiroperidol, a dopamine antagonist. However, pertussis toxin decreased the potency of (-)-NPA in the binding assay and abolished the ability of GTP to affect agonist binding. Furthermore, pertussis toxin abolished the dopamine receptor-mediated inhibition of immunoreactive alpha-melanocyte-stimulating hormone release, and induced the ADP-ribosylation of the Mr = 41,000 subunit of Ni.
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PMID:Altered activity of the inhibitory guanyl nucleotide-binding component (Ni) induced by pertussis toxin. Uncoupling of Ni from receptor with continued coupling of Ni to the catalytic unit. 608 7

In rat pars intermedia cells, the rate of alpha-melanocyte-stimulating hormone (alpha-MSH) secretion was so far known to result from a balance between the stimulatory effect of beta-adrenergic agonists and the inhibitory influence of dopaminergic substances. Recently, we have identified a second stimulatory substance, namely corticotropin-releasing factor (CRF). CRF is a potent stimulator of pars intermedia adenylate cyclase activity, cAMP accumulation and alpha-MSH release. A requirement for calcium ions was observed on basal as well as on CRF-induced alpha-MSH secretion. The beta-adrenergic and CRF effects on adenylate cyclase activity, as well as the dopamine inhibition of adenylate cyclase activity, are potentiated by guanine nucleotides (GTP). Stimulation of the beta-adrenergic receptor with isoproterenol causes a rapid loss in cAMP responsiveness, which can be completely blocked by beta-adrenergic antagonists and partially prevented by dopamine. These findings suggest that CRF should now be considered, in addition to beta-adrenergic agents, as a stimulator of the activity of pars intermedia cells and that cAMP is also involved as mediator of its action. Changes of receptor sensitivity, as well as interaction of the two stimulatory receptors with the inhibitory dopaminergic receptor, are involved in the fine control of pars intermedia cell activity. All three receptors appear to exert their action through a common pathway, namely changes of adenylate cyclase activity.
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PMID:Multiple hormonal control of pars intermedia cell activity. 619 67

The corticotropin-induced increase of total intracellular and receptor-bound cyclic AMP in isolated rat adrenocortical cells was strictly dependent on extracellular Ca(2+). A rise in bound cyclic AMP with rising Ca(2+) concentrations was accompanied by a decrease in free cyclic AMP-receptor sites. A Ca(2+)-transport inhibitor abolished the rise in bound cyclic AMP induced by corticotropin. These data suggested that during stimulation by corticotropin some Ca(2+) has to be taken up in order to promote the rise of the relevant cyclic AMP pool. In agreement with this view, adenylate cyclase activity from isolated cells proved also to be dependent on a sub-millimolar Ca(2+) concentration in the presence of corticotropin and GTP. When cells were treated under specific conditions, corticosterone production could be activated by Ca(2+) in the absence of corticotropin (cells primed for Ca(2+)). Ca(2+)-induced steroidogenesis of these cells, in the absence of corticotropin, was also accompanied by an increase in total intracellular and receptor-bound cyclic AMP, as was found previously with corticotropin-induced steroidogenesis in non-primed cells. Calcium ionophores increasing the cell uptake of Ca(2+) were not able, however, to increase the cyclic AMP pools in non-primed cells, unlike corticotropin in nonprimed cells or Ca(2+) in cells primed for Ca(2+). It was concluded that during stimulation by either corticotropin or Ca(2+) a possible cellular uptake of Ca(2+) must be very limited and directed to a specific site which may affect the coupling of the hormone-receptor-adenylate cyclase complex.
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PMID:Steroidogenic action of calcium ions in isolated adrenocortical cells. 624 83

Morphine inhibited the adenylate cyclase activity of the crude synaptosomal fraction of the rat caudate nucleus in the presence of BTP, GDP, Gpp(NH)p or ITP. The purine nucleotides themselves had an inhibitory action on the enzyme. Beta-endorphin and Met-enkephalin also inhibited the enzyme in the presence of GTP. The GTP-dependent in inhibitory action of morphine was blocked by naloxone. Various opiates and opioid peptides inhibited the enzyme by up to approximately 20 per cent in the presence of GTP. The relative potency was in higher order of levorphanol greater than beta-endorphin greater than Met-enkephalin greater than morphine greater than pentazocine. Levorphanol was about 50,000 times as potent as its biologically inactive enantiomer, dextrorphan. Morphine enhanced the inhibitory actions of GTP and GTPase-resistant Gpp(NH)p on the adenylate cyclase activity. These results suggest that GTP plays an important role in the regulation of adenylate cyclase activity in the rat caudate nucleus and that the occupation of opiate receptor by agonists inhibits the enzyme through an actual increase in the inhibitory action of GTP, rather than a suppression of the enzymatic degradation of GTP.
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PMID:Inhibition of adenylate cyclase by GTP and its modulation by opiate receptor in rat caudate nucleus. 627 23


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