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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biosynthesis of the Ca2+- and Mg2+-dependent adenosine triphosphatase of sarcoplasmic reticulum was studied in cell cultures of embryonic chick heart. Rates of synthesis were estimated from the incorporation of tritium-labeled leucine into the ATPase. Newly synthesized ATPase was isolated from cells by immunoprecipitation. Radioactive leucine incorporation into the ATPase was determined by gel electrophoresis of the immunoprecipitates and counting of gel slices containing the ATPase band. Accumulation of the ATPase was estimated from the concentration of Ca2+ and Mg2+-dependent, hydroxylamine-sensitive phosphoprotein in the whole cell membrane fraction of cultured cells. Embryonic heart cells cultured in a medium which permitted cell proliferation showed approximately linearly increasing rates of ATPase synthesis and accumulation/culture plate as the cells proliferated. When cells were cultured in a serum-free medium, cell proliferation was inhibited and there was no sustained increase in the rate of ATPase synthesis or accumulation. Inclusion of isoproterenol or dibutyryl cyclic AMP at concentrations of 10 microM up to 1 mM in serum-free culture medium failed to stimulate significantly ATPase synthesis.
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PMID:Biosynthesis of the Ca2+- and Mg2+-dependent adenosine triphosphatase of sarcoplasmic reticulum in cell cultures of embryonic chick heart. 22 35

The interactions of gadolinium ion, lithium, and two substrate analogues, beta,gamma-imido-ATP (AMP-PNP) and tridentate CrATP, with the calcium ion transport adenosine triphosphatase (Ca2+-ATPase) of rabbit muscle sarcoplasmic reticulum have been examined by using 7Li+ NMR, water proton NMR, and Gd3+ EPR studies. Steady-state phosphorylation studies indicate that Gd3+ binds to the Ca2+ activator sites on the enzyme with an affinity which is approximately 10 times greater than that of Ca2+. 7Li+, which activates the Ca2+-ATPase in place of K+, has been found to be a suitable nucleus for probing the active sites of monovalent cation-requiring enzymes. 7Li+ nuclear relaxation studies demonstrate that the binding of Gd3+ ion to the two Ca2+ sites on Ca2+-ATPase increases the longitudinal relaxation rate (1/T1) of enzyme-bound Li+. The increase in 1/T1 was not observed in the absence of enzyme, indicating that the ATPase enhances the parmagnetic effect of Gd3+ on 1/T1 of 7Li+. Water proton relaxation studies also show that the ATPase binds Gd3+ at two tight-binding sites. Titrations of Gd3+ solutions with Ca2+-ATPase indicate that the tighter of the two Gd3+-binding sites (site 1) provides a ghigher enhancement of water relaxation than the other, weaker Gd3+ site (site 2) and also indicate that the average of the enhancements at the two sites is 7.4. These data, together with a titration of the ATPase with Gd3+ ion, yield enhancements, epsilonB, of 9.4 at site 1 and 5.4 at site 2. Analysis of the frequency dependence of 1/T1 of water indicates that the electron spin relaxation taus of Gd3+ is unusually long (2 X 10(-9) s) and suggests that the Ca2+-binding sites on the ATPase experience a reduced accessiblity of solvent water. This may indicate that the Ca2+ sites on the Ca2+-ATPase are buried or occluded within a cleft or channel in the enzyme. The analysis of the frequency dependence is also consistent with three exchangeable water protons on Gd3+ at site 1 and two fast exchanging water protons at site 2. Addition of the nonhydrolyzing substrate analogues, AMP-PNP and tridenate CrATP, to the enzyme-Gd3+ complex results in a decrease in the observed enhancement, with little change in the dipolar correlation time for Gd3+, consistent with a substrate-induced decrease in the number of fast-exchanging water protons on enzyme-bound Gd3+. From the effect of Gd3+ on 1/T1 of enzyme-bound Li+, Gd3+-Li+ separations of 7.0 and 9.1 A are calculated. On the assumption of a single Li+ site on the enzyme, these distances set an upper limit on the separation between Ca2+ sites on the enzyme of 16.1 A.
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PMID:Lithium-7 nuclear magnetic resonance, water proton nuclear magnetic resonance, and gadolinium electron paramagnetic resonance studies of the sarcoplasmic reticulum calcium ion transport adenosine triphosphatase. 22 3

ATP consumption by arginyl-tRNA synthetases from Escherichia coli and Bacillus stearothermophilus has been investigated by the firefly luciferin--luciferase assay. Arginyl-tRNA synthetase from E. coli utilizes ATP only for aminocylation of tRNA with a 1:1 stoicheiometry. In contrast, we have shown an adenosine triphosphatase activity of arginyl-tRNA synthetase from B. stearothermophilus in the absence of tRNAArg. Dowex chromatography revealed the formation of ADP by the thermophile enzyme; under aminoacylation conditions, AMP was also formed in amounts stoicheiometric with arginyl-tRNA formation.
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PMID:Adenosine triphosphate consumption by bacterial arginyl-transfer ribonucleic acid synthetases. 38 95

With histochemical methods the distribution of some enzymes and metabolic substances in the epidermal peelings of Phaseolus mungo, Lathyrus sativus, and Opuntia elatior under light and dark conditions is examined. Dehydrogenases oxidases, transferases and hydrolases were studied. Fluctuations in the activity of hydrolases, especially, acid phosphatase, lipase, glucose-6-phosphatase, adenosine triphosphatase, dehydrogenases and transferases were observed during light and dark conditions. The role of such fluctuations in relation to stomatal regulation is discussed. Based on the present studies the following is suggested; stomatal opening and closing is related to structural and metabolic changes, and these changes are brought about by sugar gradients in the guard cells; light is enhancing the synthesis of sugars and some hormones, and besides this it stimulates membrane bound adenyl cyclase and release of cyclic AMP which affects the permeability; subsidiary cells actively participate in the stomatal physiology. Lysosomal hydrolytic enzymes like acid phosphatase are actively involved in catabolic phase of normal guard cells metabolism and regulate the osmotic pressure of the guard cells.
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PMID:Histochemical studies in stomatal apparatus of Phaseolus mungo Linn, Lathyrus sativus Linn and Opuntia elatior Mill. 59 72

A spin-labeled ATP analogue, 2,2,6,6-tetramethylpiperidine-1-oxyl adenosine triphosphatase (Tempo-ATP) is used to adenylate Escherichia coli glutamine synthetase (L-glutamine: ammonia ligase (ADP-forming), EC 6.3.1.2). The Tempo adenylylated glutamine synthetase (Tempo-GS) exhibits similar catalytic properties, pH profile and inhibitor susceptibility as those of glutamine synthetase adenylylated with normal ATP. Using the spin label on the enzyme as a probe and employing the spin-spin interactions between the label probe and paramagnetic Mn2+, the distances from the nitroxyl moiety of the covalently bound Tempo-AMP to the two Mn2+ binding sites, n1 and n2 were determined. The n1 site is the structural site and n2 is located at the catalytic site. The distances from Mn2+ at n1 and n2 sites to the nitroxyl radical are 19 and 16 A, respectively. Binding of the substrate, L-Glu, causes a protein conformational change which is reflected by the reduction of approximately 2 A for the n1 to Tempo-AMP distance and lengthening of approximately 2 A for the n2 to the Tempo-AMP distance. Addition of ATP to the Tempo-GS/L-Glu complex increases the distance between n1 and Tempo-AMP, and n2 and Tempo-AMP by 4 and 3 A, respectively.
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PMID:Distance changes at the regulatory and catalytic sites on Escherichia coli glutamine synthetase: a spin label study on the effect of substrate(s) binding. 167 11

We have reported previously that 2-[[[3-methyl-4-(2,2,2-trifluorethoxy)-2-pyridyl]methyl] sulfinil]- 1H-benzimidazole (AG-1749) inhibits (H+ + K+)-adenosine triphosphatase after being transformed into its cyclic sulfenamide form (AG-2000) or disulfide form (AG-1812) under acidic conditions. In this study, mechanisms related to the inhibition of acid formation by AG-1749 were investigated in isolated canine parietal cells. AG-1749 suppressed the acid formation stimulated by histamine, carbachol or dibutyryl cyclic AMP with IC50 values of approximately 0.09 microM: AG-1749 being twice as potent as omeprazole. The inhibitory effect of AG-1749 was antagonized by dithiothreitol (1 mM). 2-Cyclo-hexen-1-one (3 mM) decreased cytosolic glutathione to less than 10% of control value, and caused a 3-fold increase in the inhibitory effect of AG-1749. Glutathione, however, when added exogenously, did not affect the action of AG-1749. The inhibition was reversed by removing AG-1749 from the medium or by adding dithiothreitol (1 mM). The reversal of inhibition by these two procedures was hardly affected by puromycin (100 microM) or cycloheximide (300 microM) but significantly prevented by 2-cyclo-hexen-1-one (1 mM). Exogenously added AG-2000 (10 microM) or AG-1812 (5 microM), active forms of AG-1749, did not inhibit acid formation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Possible mechanism for the inhibition of acid formation by the proton pump inhibitor AG-1749 in isolated canine parietal cells. 215 97

Determination of kinetic properties for kinesin adenosine triphosphatase (ATPase), a proposed motor for transport of membranous organelles, requires adequate amounts of kinesin with a consistent level of enzymatic activity. A purification procedure is detailed that produces approximately 2 mg of kinesin at up to 96% purity from 800 g of bovine brain. This protocol consists of a microtubule affinity step using 5'-adenylylimidodiphosphate (AMP-PNP); followed by gel filtration, ion exchange, and hydroxylapatite chromatography; and then sucrose density gradient centrifugation. The microtubule-activated ATPase activity of kinesin coeluted with kinesin polypeptides throughout the purification. Highly purified kinesin had a Vmax of 0.31 mumol/min/mg in the presence of microtubules, with a Km for ATP of 0.20 mM. The kinetic constants obtained in these studies compare favorably with physiological levels of ATP and microtubules. Variations in buffer conditions for the assay were found to affect ATPase activity significantly. A study of the ability of kinesin to utilize a variety of cation-ATP complexes indicated that kinesin is a microtubule-stimulated Mg-ATPase, but kinesin is able to hydrolyze Ca-ATP, Mn-ATP, and Co-ATP as well as Mg-ATP in the presence of microtubules. In the absence of microtubules, Ca-ATP appears to be the best substrate. Studies with several inhibitors of ATPases determined that vanadate inhibited kinesin ATPase at the lowest concentrations of inhibitor, but significant inhibition of the ATPase also occurred with submillimolar concentrations of AMP-PNP. Other inhibitors of kinesin include N-ethylmaleimide, adenosine diphosphate (ADP), pyrophosphate, and tripolyphosphate. Further characterization of the kinetic properties of the kinesin ATPase is important for understanding the molecular mechanisms for transport of membranous organelles along microtubules.
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PMID:Copurification of kinesin polypeptides with microtubule-stimulated Mg-ATPase activity and kinetic analysis of enzymatic properties. 252 82

Vanadate has been used in many cellular systems to elucidate mechanisms of enzyme action. Vanadate inhibits Na-K adenosine triphosphatase (ATPase) activity in many tissues. In isolated collecting tubule it inhibits sodium transport and vasopressin-stimulated water flux, the latter presumably distal to cyclic AMP formation. Depending upon the tissue studied, vanadate also stimulates a variety of cellular reactions including adenylate cyclase, glucose oxidation and glycogen synthesis. We studied the effect of varying concentrations of vanadate on N-ethylmaleimide (NEM)-sensitive ATPase activity in microdissected segments of rat nephron. In proximal convoluted tubule and in cortical, medullary and papillary collecting ducts vanadate had no effect on enzyme activity. In medullary and cortical thick ascending limbs, however, vanadate significantly stimulated NEM-sensitive ATPase activity (medullary thick ascending limb, 241 +/- 14 pmol/mm/hr vs. 531 +/- 74 pmol/mm/hr; control vs. (1 mM) vanadate, respectively; n = 14, P less than 0.01). The stimulatory effect of vanadate on NEM-sensitive ATPase activity was present at 5 microM vanadate, a concentration that inhibited Na-K ATPase activity approximately 80%. Metabolic acidosis also stimulated enzyme activity in the thick ascending limb, and the effect of vanadate was not additive. Metabolic alkalosis had no effect on NEM-sensitive ATPase in the thick ascending limb, but the stimulatory effect of vanadate was still seen. These data document that the NEM-sensitive ATPase in thick ascending limb is different from that found in other nonmammalian proton secretory epithelia which are vanadate inhibitable. The results with vanadate plus metabolic acidosis suggest that both are acting via the same mechanism.
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PMID:Vanadate stimulates the N-ethylmaleimide-sensitive adenosine triphosphatase in rat nephron. 252 98

The antisecretory and antiulcer activities of 2[[[3-methyl-4-(2,2,2-trifluoroethoxy)-2-pyridyl]methyl] sulfinyl]-1H-benzimidazole (AG-1749) were investigated in dogs and rats. AG-1749 inhibited both the (H+ + K+)-adenosine triphosphatase activity in canine gastric microsomes and dibutyryl cyclic AMP-stimulated acid formation in isolated canine parietal cells and suppressed the acid secretion stimulated by histamine, pentagastrin, bethanechol or a peptone meal in Heidenhain pouch dogs; the ID50 values were between 0.2 and 0.7 mg/kg p.o. AG-1749 inhibited both the histamine-stimulated and the basal acid secretion in pylorusligated rats and prevented water immersion stress or aspirin-induced gastric lesions and mepirizole or cysteamine-induced duodenal ulcers in rats; the ID50 values were between 0.3 to 3.6 mg/kg p.o. or i.d. Furthermore, AG-1749 prevented gastric lesions induced by absolute ethanol or acidified aspirin, and accelerated the healing of acetic acid-induced gastric or duodenal ulcers in rats. The inhibitory potency of AG-1749 in dogs was much the same as that of omeprazole and about half that of ranitidine. However, it was about 2 to 10 times more potent than omeprazole and 4 to 34 times more potent than ranitidine in rats. These results suggest that AG-1749 exerts prominent antiulcer activities mainly by suppressing acid secretion via an inhibition of a proton pump in gastric parietal cells and partly by protecting the gastrointestinal mucosa against various ulcerative stimuli.
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PMID:Antisecretory and antiulcer activities of a novel proton pump inhibitor AG-1749 in dogs and rats. 253 18

Several studies suggested that catecholamines modulate renal sodium and water excretion by direct stimulation of adrenergic receptors located on the renal proximal tubule. However, neither the mechanism nor the class of adrenoceptor involved in this effect have yet been established definitively. In the present study, we examined the effects of L-norepinephrine (NE) and selective alpha-1, alpha-2 and beta adrenergic agonists on monovalent cation transport and on Na+-K+-adenosine triphosphatase (ATPase) activity from homogenates, intact tubules and highly purified basolateral membranes prepared from superficial rabbit kidney cortex. Our results showed that neither NE nor specific alpha-1, alpha-2 and beta adrenergic agonists (10 microM) modified ouabain-sensitive uptake of 86Rb+ (a K+ analog) in intact proximal tubules. Similarly, it is demonstrated that NE and alpha and beta adrenergic agonists did not affect Na+-K+-ATPase activity from homogenates, intact tubules and basolateral membranes. The integrity of the alpha-2 adrenergic receptor system, the predominant adrenergic subtype in rabbit proximal tubule, was supported by the following findings: 1) maximal binding of [3H] rauwolscine was about 4-fold higher in basolateral membranes than in homogenates; 2) 5'-guanylimidodiphosphate induced a 27-fold increase in the Ki of NE for alpha-2 receptor in basolateral membranes; 3) NE (5 microM) inhibited by 35% parathyroid hormone-stimulated cyclic AMP production in intact tubules. In conclusion, these data fail to demonstrate that NE, as well as other adrenergic agonists, directly increases Na+-K+-ATPase in the rabbit proximal tubule. Further investigations are needed to clarify the interaction of catecholamines with the renal Na+K+ pump.
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PMID:Adrenergic agonists and the Na+-K+-adenosine triphosphatase from rabbit proximal tubules and their basolateral membranes. 254 43


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