Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Purified bovine pituitary plasma membranes possess two specific LH-RH binding sites. The high affinity site (2.5 X 10(9) l/mol) has low capacity (9 X 10(-15) mol/mg membrane protein) while the low affinity site 6.1 X 10(5) l/mol) has a much higher capacity (1.1 X 10(-10) mol/mg). Specific LH-RH binding to plasma membranes is increased 8.5-fold during purification from homogenate whilst adenylate cyclase activity is enriched 7--8-fold. Distribution of specific LH-RH binding to sucrose density gradient interface fractions parallels that of adenylate cyclase activity. Mg2+ and Ca2+ inhibit specific [125I]LH-RH binding at micromolar concentrations. Synthetic LH-RH, up to 250 microgram/ml, failed to stimulate adenylase cyclase activity of the purified bovine membranes. Using a crude 10,800 g rat pituitary membrane preparation, LH-RH similarly failed to activate adenylate cyclase even in the presence of guanyl nucleotides. These data confirm the presence of LH-RH receptor sites on pituitary plasma membranes and suggest that LH-RH-induced gonadotrophin release may be mediated by mechanisms other than activation of adenylate cyclase.
Mol Cell Endocrinol 1978 Jun
PMID:LH-RH binding to purified pituitary plasma membranes: absence of adenylate cyclase activation. 21 61

Specific receptors for thyrotropin were found to exist in membranes from whole human subcutaneous fat tissue. The characteristics of the interaction of 125I-labelled thyrotropin with such receptors were determined and compared with the stable, high-affinity thyrotropin receptor shown previously to exist in guinea pig fat membranes. Specific binding was readily detectable using low concentrations of membranes (up to 80 microgram/ml), though specific binding was reduced at higher membrane concentrations. Increasing concentrations of unlabelled thyrotropin reduced fractional binding, revealing saturation of a population of mixed affinity sites (highest Ka of the order of 0.3 X 10(9) M-1). Little cross-reactivity was observed with other lipolytic or structurally related hormones, though some cross-reactivity was observed in the presence of human chorionic gonadotropin. Association was temperature-dependent and rapid at 37 degrees C, though prolonged incubation revealed some instability of binding at this temperature. Binding was reversible with a high dissociation rate constant, and was particularly sensitive to the presence of low concentrations of sodium or calcium ions. Using membranes prepared from isolated human fat cells, binding of thyrotropin was equally sensitive to the addition of cations.
Mol Cell Endocrinol 1978 Oct
PMID:Characterization of thyrotropin binding to specific receptors in human fat tissue. 21 61

The binding sites for aldosterone and a potent aldosterone antagonist (SC-26304) were studied in kidney cytosol from adrenalectomized rats. Preformed cytosol and kidney slices were incubated with 3H-labeled steroids in a wide range of concentrations. The recovery and characteristics of the binding sites were affected by the incubation and homogenization conditions. High-affinity, Type I mineralocorticoid binding was reduced by more than 95% when cytosol was incubated at 25 degrees C in the presence of calcium. Tissue dilution also affected the binding sites. SC-26304 was bound to high- and low-affinity receptors, similar to the binding of aldosterone. The physiologic response to aldosterone could result from binding to either or both sets of sites. Some of the physiologic responses to spirolactones could represent antagonism of the binding of aldosterone to either or both sites. A convenient method is presented for describing the relative occupancy of several different sites by any particular steroid.
Mol Cell Endocrinol 1978 Nov
PMID:Occupancy of aldosterone binding sites in rat kidney cytosol. 21 76

Carbamylcholine and acetylcholine through a muscarinic type of receptor, KCl, ionophore A-23187 and NaF increased cyclic GMP accumulation in dog-thyroid slices. These effects were abolished in calcium-depleted slices, which findings confirm that Ca2+ is required for cyclic GMP accumulation. All these agents depressed the accumulation of cyclic AMP in TSH-stimulated slices. KCl and NaF depressed cyclic AMP accumulation in TSH-treated slices even when they had been depleted of Ca2+. This suggests a cyclic GMP- and Ca2+-independent mechanism. The absence of inhibition of the effects of the ionophore, NaF and KCl in the presence of atropine suggests that these drugs do not act by inducing the release of acetylcholine in the slices. The effects of carbamylcholine and ionophore A-23187 on cyclic GMP accumulation and protein iodination were reversible; the inhibitions of TSH-induced cyclic AMP accumulation and secretion were non-competitive and were not accompanied by a depression of ATP levels. All these effects were greatly decreased in the absence of extracellular Ca2+. These data suggest that carbamylcholine and ionophore A-23187 act mainly by increasing the influx of extracellular Ca2+ in thyroid cells. However, the persistence of some carbamylcholine effect in the absence of Ca2+ in the medium suggests that this agent may also trigger the release of Ca2+ from an intrafollicular pool. The kinetics of action of carbamylcholine are compatible with a role of cyclic GMP in the inhibition of cyclic AMP accumulation. However, with the ionophore, the depression of cyclic AMP accumulation was much longer than the rise of cyclic GMP, which suggests a mechanism independent of cyclic GMP.
Mol Cell Endocrinol 1979 Apr
PMID:Effects of carbamylcholine and ionophore A-23187 on cyclic 3',5'-AMP and cyclic 3',5'-GMP accumulation in dog-thyroid slices. 22 40

Cyclic AMP-dependent protein kinase has been well established to be composed of catalytic and regulatory subunits, and cyclic AMP acts to dissociate these subunits to exhibit full enzymatic activity. In contrast, cyclic GMP-dependent protein kinase does not possess such a subunit structure and is activated by cyclic GMP simply in an allosteric manner. In addition to cyclic AMP-dependent and cyclic GMP-dependent protein kinases, another species of multifunctional protein kinase has been found in many mammalian tissues. This protein kinase is entirely independent of cyclic nucleotides and activated by lower concentrations of Ca2+ in the presence of a membrane-associated factor. This factor has been identified as phospholipids; in fact, phosphatidylinositol and phosphatidylserine are active in this role, whereas lecithin and sphingomyelin are unable to activate the enzyme. Thus, the three species of protein kinases mentioned above are activated in different manners. Nevertheless, these enzymes show very similar substrate specificities and phosphorylate the same specific seryl residues of histone fractions. In addition, all enzymes have abilities to activate and inactivate muscle phosphorylase kinase and glycogen synthetase, respectively, although the relative rates of reactions towards various substrates are markedly different. The Ca2+-dependent protein kinase seems to be associated with membranous components, whereas cyclic GMP-dependent protein kinase appears to be related to certain subcellular organella such as nucleus. Suggestive evidence is available implying that the cyclic AMP-, cyclic GMP- and Ca2+-activated three sets of protein kinase systems may play each specific physiological roles presumably owing to their own subcellular compartments.
Mol Cell Biochem 1979 Feb 09
PMID:Regulatory and functional compartment of three multifunctional protein kinase systems. 22 57

Histone kinase activity was purified from human polymorphonuclear leukocytes by ammonium sulphate precipitation of a 180 000 x g supernatant, followed by DEAE-cellulose chromatography and gelfiltration. On DEAE-cellulose cAMP dependent kinase activity eluted in two peaks, I and III, at 1.2 mmho and 6.5 mmho, respectively. Catalytic subunit (C) from both peaks had Mr 33 000, 3.0S. Regulatory subunit (R) from peak I and III both had Mr 33 000 upon gelfiltration, but sedimented at 2.8--3.0S and 3.0--3.2S, respectively. R2 and R4 subunits were identified. The R-C dimer from peak I and III sedimented at 4.8S and (4.8)--5.1S, respectively. The holoenzyme from peak I had Mr 165 000, 6.7S, which suggest a R2C2 structure, while that of peak III sedimented at 6.7S, but eluted at Mr 330 000 (2R2C2) by gelfiltration. The Kmapp for peak I and III enzymes were, respectively: histone IIA 0.5 mg/ml (both forms), ATP 18 microM and 23 microM, and cAMP 5 X 10(-8) M and 6.3 x 10(-8) M. Both enzymes had pH optimum 6.7--6.9 and were equally sensitive to Ca2+, temperature and protein kinase inhibitor. The substrate specificity was histone VS greater than histone IIA = histone VIS greater than casein greater than phosvitin. Peak I enzyme, but not peak III enzyme, was dissociated by histone and high ionic strength and reassociation of R and C subunits were facilitated by ATP-Mg. It is concluded that peak I and III enzymes represent type I and II cAMP dependent protein kinases, respectively. Type I comprises 20--30% of cAMP dependent protein kinase activity and is absent from the 180 000 x g supernatant of gently disrupted cells. Purified catalytic subunit had Kmapp (ATP) 20 microM with rabbit muscle glycogen synthease I as substrates. Synthase I from rabbit muscle and human leukocytes were phosphorylated by catalytic subunit to synthase D (ratio of independence less than 0.07). cAMP independent histone kinase activity eluted in one peak (Peak II) at3 mmho. The enzymatic activity sedimented at 3.4S and eluted from gelfiltration with Mr 78 000. Kmapp for ATP was 78 microM and for histone IIA 0.5 mg/ml. The enzyme was sensitive to temperature, but less sensitive than cAMP dependent protein kinase to Ca2+, and insensitive to protein kinase inhibitor. The substrate specificity was histone IIA greater than histone VS = histone VIS, while casein and phosvitin were poor substrates. Glycogen synthase I was not phosphorylated. The cAMP independent histone kinase activity comprised 15% of the total histone kinase activity in a crude homogenate of leukocytes. Its physiological substrate is unknown.
Mol Cell Biochem 1979 Jul 15
PMID:Purification and properies of cAMP dependent and independent histone kinases from human leukocytes. 22 66

The phosphorylation of proteins in the synaptic plasma membrane is a rather slow reaction taking several minutes to saturate all the phosphate acceptor sites. (The time for half the protein bound phosphate groups to turnover is about 1 min). A divalent cation is needed as a cofactor for the reaction. At high (0.5 mM) ATP concentrations Mg2+ is more effective than Mn2+ but at low (10 microM) ATP concentrations the reverse is the case. Zn2+ and Ca2+ support very little phosphorylation.
Mol Cell Biochem 1979 Oct 15
PMID:The time course of the phosphorylation of proteins in the synaptic plasma membrane and the effect of certain cations. 22 75

Calcium, in partnership with cyclic AMP, controls the proliferation of non-tumorigenic cells in vitro and in vivo. While it does not seem to be involved in the proliferative activation of cells such as hepatocytes (in vivo) or small lymphocytes (in vitro), it does control two later stages of prereplicative (G1) development. It must be one of the very many regulatory and permissive factors affecting early prereplicative development, because severe calcium deprivation reversibly arrests some types of cell early in the G1 phase of their growth-division cycle in vitro. However, calcium more specifically and much more often regulates a later (mid or late G1) stage of prereplicative development. Thus, regardless of its severity or the type of cell, calcium deprivation in vitro or in vivo reversibly stops proliferative development at that part of the G1 phase in which the cellular cyclic AMP content transiently rises and the synthesis of the four deoxyribonucleotides begins. The evidence points to calcium and the cyclic AMP surge being co-generators of the signal committing the cell to DNA synthesis. The evidence is best explained so far by the cyclic AMP surge causing a surge of calcium ions which combine with molecules of the multi-purpose, calcium-dependent, regulator protein calmodulin (CDR) somewhere between the cell surface and the cytosol. The resulting Ca-calmodulin complexes then stimulate many different (and possibly membrane-associated) enzymes such as protein kinases, one of which produces the DNA-synthetic initiator. Calcium has little or no influence on the proliferation of tumor cells. Some possible explanations of this very important loss of control are considered.
Mol Cell Biochem 1979 Nov 01
PMID:The regulation of cell proliferation by calcium and cyclic AMP. 22 7

1. Ionized calcium, protein-bound calcium and total calcium in serum were measured in patients receiving haemodialysis treatment. 2. During dialysis, the ionized calcium fraction decreased and the bound calcium increased. The blood pH also increased. 3. Studies in vitro suggested that the fall in ionized calcium and rise in protein-bound calcium were larger than could be explained by the redistribution of calcium fractions due to the pH change. 4. An explanation could be that haemodialysis increases calcium binding by serum proteins. Such an effect may be implicated in the aetiology of hyperparathyroidism and bone disease in patients undergoing haemodialysis.
Clin Sci Mol Med Suppl 1975 Jun
PMID:Changes in protein-bound calcium in the serum of haemodialysis patients. 23 48

The bacterium Pseudomonas phaseolicola was successfully transformed, for the first time, with R-factors RSF1010 and pBR322 DNA by a calcium-shock and heat-pulse technique. Frequency of transformation for RSF1010 ranged from 0.8 x 10(-7) to 3.1 x 10(-6) and was ca. 0.4 x 10(-8) for pBR322.
Mol Gen Genet 1979 Jul 02
PMID:Genetic transformation of Pseudomonas phaseolicola by R-factor DNA. 28


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