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)

The enzyme, myosin light chain kinase, has been purified to homogeneity from bovine aortic vascular smooth muscle. Approximately 10 mg of enzyme could be obtained from 1 kg of fresh aortas with an overall yield of 26% of the original activity. The vascular myosin light chain kinase has a molecular weight of 160 000 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Antiserum raised to the aortic myosin light chain kinase in rabbits strongly inhibited phosphotransferase activity. In addition, the antiserum was used to identify myosin kinase in a crude homogenate of vascular smooth muscle by radioimmunoblotting. A single species of the enzyme (Mr = 160 000) was identified. The bovine aortic myosin kinase could be phosphorylated by both cyclic AMP- and GMP-dependent protein kinases. Approximately 2 mols PO4/mole of enzyme could be incorporated by the cyclic AMP-dependent protein kinase in the absence of calmodulin. If Ca2+ and calmodulin were included in the reaction mixture, phosphate incorporation by the cyclic AMP-dependent protein kinase was reduced to 1 mol and phosphorylation by cyclic GMP-dependent protein kinase was completely inhibited. These results were confirmed by tryptic peptide mapping. Two distinct phosphopeptides were identified: site-1 and site-2. Both could be phosphorylated by the cyclic AMP-dependent protein kinase but only site-1 was phosphorylated by the cyclic GMP-dependent enzyme. In the presence of Ca2+ and calmodulin, phosphorylation by cAMP-dependent protein kinase was restricted to site-1. The effect of phosphorylation on myosin light chain kinase activity was determined. Only phosphorylation by cyclic AMP-dependent protein kinase was found to alter the requirement of myosin kinase for calmodulin. The K0.5 (i.e. the concentration of calmodulin required for half-maximal enzyme activation) for calmodulin was 5 nM for the unphosphorylated myosin kinase. With 2 mol PO4/mol myosin kinase incorporated, the K0.5 for calmodulin was increased to 82 nM. When only 1 mol PO4/mol myosin kinase was incorporated, no effect on calmodulin requirement was observed. Moreover, single site phosphorylation had no effect on other activity parameters, including Km for ATP and for light chains. Our studies suggest that cyclic AMP-dependent protein kinase may play an important role in the regulation of vascular myosin kinase activity. Moreover, our results indicate that cyclic GMP-dependent protein kinase does not affect calmodulin-activation of myosin kinase or several other activity parameters.
J Mol Cell Cardiol 1985 Sep
PMID:Phosphorylation of myosin light chain kinase from vascular smooth muscle by cAMP- and cGMP-dependent protein kinases. 299 88

The tridecapeptide, neurotensin, inhibited prostaglandin E1-stimulated cyclic AMP production in intact plated neuroblastoma N1E115 cells. The peptide effect was concentration dependent (EC50 = 2 nM) and maximal inhibition reached 55% with 100 nM neurotensin. Acetyl neurotensin (8-13) was as active as neurotensin whereas neurotensins (1-8), (1-12), and (10-13) were barely active in inhibiting cyclic AMP production, thus showing the requirement of the carboxy terminal hexapeptide sequence of neurotensin for biological activity. The inhibitory effect of neurotensin on cyclic AMP production was largely prevented by pretreatment of N1E115 cells with islet-activating protein (pertussis toxin). In contrast, pertussis toxin did not inhibit neurotensin-stimulated cyclic GMP production in neuroblastoma cells. In cell membranes, the toxin promoted the selective ADP-ribosylation of a single protein having the same molecular weight (41,000) as the alpha-subunit of Ni, the inhibitory regulatory protein of adenylate cyclase. In membranes prepared from N1E115 cells, monoiodo[125I-Tyr3]neurotensin bound to a single population of receptors characterized, at 25 degrees and in the absence of monovalent cations and guanyl nucleotides, by a dissociation constant (Kd) of 56 pM and a maximal binding capacity (Bm) of 30 fmol/mg of protein. Na+ (10-100 mM) and GTP (0.1-100 microM) inhibited neurotensin binding in a concentration-dependent manner. At 100 mM Na+ and 100 microM GTP, receptor affinity was decreased by 5- and 2-fold, respectively. Li+ and K+ were less effective than Na+, and the effect of GTP was shared by GDP and guanyl-5'-yl-imidodiphosphate, but not by GMP, ATP, ADP, or adenyl-5'-yl-imidodiphosphate. It is concluded that in N1E115 cells, neurotensin attenuates cyclic AMP production by exerting an inhibitory effect on adenylate cyclase through an interaction of the peptide receptors with the regulatory GTP-binding protein Ni.
Mol Pharmacol 1986 May
PMID:Neurotensin-mediated inhibition of cyclic AMP formation in neuroblastoma N1E115 cells: involvement of the inhibitory GTP-binding component of adenylate cyclase. 301 77

AMP deaminase, the activity that catalyzes the deamination of AMP to form IMP and NH3 has been measured in Dictyostelium discoideum. A new procedure to assay the activity of this enzyme was developed using formycin 5'-monophosphate, a fluorescent analog of AMP as the substrate, and ion-paired reverse phase HPLC to separate the reactants and products. Quantitation of the formycin containing compounds was accomplished at 290 nm. At this wavelength adenosine containing compounds were not detected and activity could be monitored in the presence of its activator ATP. The AMP deaminase activity in vegetative cells was 7.4 nmols/min/mg proteins while the activity in cells measured at 2 and 6 hrs after starvation-induced growth-arrest was 376 nmols/min/mg protein...a 51-fold increase. When vegetative cells were treated with hadacidin, a drug that restricts de novo AMP synthesis and pinocytosis, the activity of the AMP deaminase was 511 nmols/min/mg protein...a 70-fold increase compared to that in untreated vegetative cells. Smaller increases were noted following the inhibition of growth with the drugs cerulenin and vinblastine, as well as after the inhibition of de novo GMP synthesis with the drug mycophenolic acid or the partial inhibition of de novo AMP synthesis with analogs of hadacidin, N-hydroxyglycine and N-formylglycine. In addition, when the activity of two other enzymes involved in purine metabolism, namely adenosine kinase and hypoxanthine-guanine phosphoribosyl transferase, was measured in vegetative cells, and the activity of both compared to that measured in starvation and hadacidin induced growth-arrested cells, showed no significant changes.(ABSTRACT TRUNCATED AT 250 WORDS)
Mol Cell Biochem 1986 Jun
PMID:AMP deaminase in Dictyostelium discoideum: increase in activity following nutrient deprivation induced by starvation or hadacidin. 301 11

ADP ribosylation of membranes by pertussis toxin (PT) and cholera toxin (CT) was studied as a function of addition of ATP, various guanine nucleotides, Mg2+, and inorganic phosphate (Pi). ADP ribosylation of a 40 kilodalton (kDa) band by PT is markedly enhanced by ATP and GTP and is strongly inhibited by Pi or Mg2+. GTP analogs (GTP gamma S and GMP-adenyl-5'-yl imidodiphosphate) were less effective. In contrast, ADP ribosylation of two substrates for CT (of 42 and 50 kDa) is stimulated by Pi, Mg2+, and GTP or GTP analogs such as GTP gamma S, but is unaffected by ATP. These stimulatory conditions correlate well with GTP-mediated activation of stimulated nucleotide-binding regulatory component of adenyl cyclase. Optimal conditions for ADP ribosylation by PT do not correlate simply with conditions thought to lead to stabilization of an inactive form of inhibitory nucleotide-binding regulatory component of adenyl cyclase (Gi) or Gi-like protein; rather, the data suggest the involvement of both a stimulatory nucleotide site on PT (positively affected by either ATP or GTP) and a stabilizing site on the PT substrate (affected by GDP, GDP beta S, or GTP). Treatment of membranes with Lubrol PX increased ADP ribosylation by PT by as much as 25- to 30-fold, but inhibited the action of CT. Using defined conditions for ADP ribosylation by PT and CT, distinct labeling patterns were observed in thyroid, brain, corpus luteum, liver, heart, and erythrocytes membranes. All membranes were more intensely labeled by PT rather than CT.
Mol Endocrinol 1987 Jul
PMID:Adenosine diphosphate ribosylation of G proteins by pertussis and cholera toxin in isolated membranes. Different requirements for and effects of guanine nucleotides and Mg2+. 315 63

Comparison has been made of the proton magnetic resonance (PMR) spectra of translating ribosomes in the pre-translocation and post-translocation states as well as of the complexes of translating ribosomes with elongation factors Tu (EF-Tu) or G (EF-G) in the presence of the uncleavable analogue of GTP--guanylyl-imidodiphosphate (GMP-PNP). It is shown that proteins L7/L12 within the translating ribosomes possess a high intramolecular mobility both in the pre-translocation and in the post-translocation states. The interaction of EF-G with translating ribosomes results in a decrease of the mobility of the L7/L12 proteins. The interaction of EF-Tu with translating ribosomes leads to slight changes in the PMR spectra different from the changes caused by EF-G.
Mol Biol (Mosk)
PMID:[Structural analysis of translating ribosomes. Proton magnetic resonance method]. 318 29

Rats with superluteinized ovaries were injected with the prostaglandin F2 alpha (PGF2 alpha) analogue cloprostenol to induce luteolysis. The treatment led to decreased adenylyl cyclase response to hCG and isoproterenol in ovarian homogenates while the response to forskolin remained unchanged indicating that the catalytic unit of the enzyme was not affected by the treatment. The activation of adenylyl cyclase by Mg2+ or the non-hydrolysable guanosine triphosphate (GTP) analogue guanosine-5'-(beta,gamma-imido)-triphosphate (GMP-P(NH)P) was not altered by the treatment with cloprostenol. Both basal and hormone-stimulated adenylyl cyclase activity increased with increasing concentration of GMP-P(NH)P. Unstimulated adenylyl cyclase continuously increased with increasing concentrations of Mg2+. The same applied to forskolin. The dependence of the adenylyl cyclase stimulation by hCG and isoproterenol on Mg2+ was complex. It is postulated that PGF2 alpha induces the attenuation of ovarian adenylyl cyclase by a modification in the coupling of the hormone-receptor to the N beta-component of the adenylyl cyclase complex while the catalytic unit remains unchanged.
Mol Cell Endocrinol 1986 Mar
PMID:Characterization of the adenylate cyclase of the rat corpus luteum during luteolysis induced by a prostaglandin F2 alpha analogue. 395 53

The influence of an acute exposure to ethanol on adenylyl cyclase activity in membrane fractions prepared from human corpus luteum was investigated. Ethanol up to a concentration of 5% (v/v) was without effect on basal luteal adenylyl cyclase activity, but markedly potentiated stimulation of NaF and hCG in a dose-dependent manner. In contrast, ethanol progressively inhibited forskolin stimulation at the same range of ethanol concentrations. Maximal NaF and hCG responsiveness of adenylyl cyclase activity was observed at 5% ethanol and reached values 80% and 100% higher than controls without ethanol, respectively. However, at the same ethanol concentration, forskolin-stimulated enzymatic activity was reduced by 40% relative to controls. Equilibrium binding studies involving [125I]hCG interaction with luteal membranes in the presence of the concentration of ethanol showing maximal hCG responsiveness indicated that ethanol slightly affected (15% increase) the hCG binding compared to controls, without any appreciable change on the Kd for the hormone. This minor effect of ethanol on gonadotropin binding sites contrasted greatly with the extent at which ethanol maximally potentiated the gonadotropin-stimulated adenylyl cyclase. GTP was found to be less effective than GMP-P(NH)P in sustaining ethanol potentiation, suggesting that ethanol is unlikely to act by inhibiting GTPase activity. These data indicate that the acute effects of ethanol inhibit forskolin-stimulated adenylyl cyclase at concentrations potentiating stimulatory effects of NaF and of hCG, and that the synergistic interaction of ethanol and gonadotropin stimulation of adenylyl cyclase is, at least in part, due to an increase in the functional coupling of the occupied hCG-receptor complex with the components of the enzyme system.
Mol Cell Endocrinol 1985 May
PMID:Opposite effects of ethanol on the activation of adenylyl cyclase in human corpus luteum membranes. 404 41

Treatment of gp18, a biologically active monomer of the structural protein of the bacteriophage T4 contractile sheath, with 0.6 M-HClO4 leads to the release of GDP, GMP and inorganic phosphate. Each gp18 molecule is shown to carry three atoms of phosphorus. In the isolated protein preparation, gp18 and the nucleoside phosphate are in equimolar relation. It is suggested that in the native sheath-protein subunit, GDP and inorganic phosphate are united as GTP.
J Mol Biol 1984 Nov 05
PMID:On the presence of guanosine phosphate in the tail of bacteriophage T4. 609 55

Guanine is transported into germinated conidia of Neurospora crassa by the general purine base transport system. Guanine uptake is inhibited by adenine and hypoxanthine but not xanthine. Guanine phosphoribosyltransferase (GPRTase) activity was demonstrated in cell extracts of wild-type germinated conidia. The Km for guanine ranged from 29 to 69 micro M in GPRTase assays; the Ki for hypoxanthine was between 50 and 75 micro M. The kinetics of guanine transport differ considerably from the kinetics of GPRTase, strongly suggesting that the rate-limiting step in guanine accumulation in conidia is not that catalyzed by GPRTase. Efflux of guanine or its metabolites appears to have little importance in the regulation of pools of guanine or guanine nucleotides since very small amounts of 14C label were excreted from wild-type conidia preloaded with [8-14C]guanine. In contrast, excretion of purine bases, hypoxanthine, xanthine, and uric acid appears to be a mechanism for regulation of adenine nucleotide pools (Sabina et al., Mol. Gen. Genet. 173:31-38, 1979). No label from exogenous [8-14C]guanine was ever found in any adenine nucleotides, nucleosides, or the base, adenine, upon high-performance liquid chromatography analysis of acid extracts from germinated conidia of wild-type of xdh-l strains. The 14C label from exogenous [8-14C]guanine was found in GMP, GDP, GTP, and the GDP sugars as well as in XMP. Xanthine and uric acid were also labeled in wild-type extracts. Similar results were obtained with xdh-l extracts except that uric acid was not present. The labeled xanthine and XMP strongly suggest the presence of guanase and xanthine phosphoribosyltransferase in germinated conidia.
 ...
PMID:Guanine uptake and metabolism in Neurospora crassa. 617

Glutamyl- and lysyl-tRNA synthetase activities in total preparations and high-molecular complexes from rat liver increase 21 h after partial hepatectomy. Glutamyl-tRNA synthetase has been highly purified from normal and regenerating liver. Km, Vmax values and molecular activity were practically the same for both enzyme preparations. Total methyltransferase activity and that as a part of high-molecular complexes increase 1.5 fold 21 h after the operation but the changes of individual methyltransferase activities differ. The level of tRNA methylation in vivo is also higher during regeneration. Proteinkinases of high-molecular complexes from regenerating liver are sensitive to cyclic AMP and GMP in contrast to control.
Mol Biol (Mosk)
PMID:[Aminoacyl-tRNA-synthetases and their high molecular weight complexes in the regenerating rat liver]. 620 49


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