Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membrane vesicles from Azotobacter vinelandii O prepared by osmotic lysis of spheroplasts in tris (hydroxymethyl) aminomethane/acetate buffer (pH 7.8) contain a latent adenosine triphosphatase (ATPase). The ATPase can be activated when the vesicles are incubated in the presence of an electron donor (D-lactate) and a mixture of adenosine diphosphate and inorganic phosphate or by controlled treatment with trypsin. After the ATPase is activated, the membrane vesicles in the presence of adenosine triphosphate accumulate calcium but not glucose or rubidium (in the presence of valinomycin). ATP-dependent calcium uptake follows Michaelis-Menten kinetics with a Km of 48 muM and a Vmax of 20 nmol/min/mg of membrane protein and is highly specific for calcium over cations magnesium, barium, lanthanum, sodium, potassium, and lithium. The calcium accumulated in the presence of ATP is freely exchangeable with external calcium and is rapidly released in the presenceof uncouplers or ATPase inhibitors. Calcium uptake in the presenceof ATP is blocked by dicyclohexylcarbodiimide, ADP, p-chloromercuriphenylsulfonate, by the proton-conducting ionophores m-chlorophenylcarbonylcyanide hydrazone, nigericin, monensin, and gramicidin D, but not by potassium cyanide, anoxia, or valinomycin (in the presence of potassium). Measurements of the external pH of vesicle suspensions reveal that protons are actively taken up by the membranes during hydrolysis of ATP. These results suggest that vesicles prepared under these conditions have a topology which is inverted with respect to the intact cell and that calcium is accumulated by means of proton antiport.
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PMID:ATP-dependent calcium transport in isolated membrane vesicles from Azotobacter vinelandii. 0 92

Native solium and potassium adenosine triphosphatase from guinea pig kidney accepted a phosphate group from radioactive inorganic phosphate to form an acyl phosphate bond at the active site in the presence or absence of sodium ion. Magnesium ion was always required. In the presence of sodium ion and absence of adenosine triphosphate, there was no phosphorylation by inorganic phosphate. Addition of unlabeled adenosine triphosphate produced a potassium-sensitive phosphoenzyme which exchanged its phosphate-group with radioactive inorganic phosphate. The dephosphoenzyme was an intermediate in this exchange. The rate constant for dephosphorylation was about 0.05 per second. Addition of rubidium ion, a congener of potassium ion, to the potassium-sensitive phosphoenzyme produced a phosphoenzyme labeled from inorganic phosphate with a corresponding rate constant of 0.26 per s. This was a rubidium-complexed phosphoenzyme. Addition of magnesium ion to potassium-sensitive phosphoenzyme converted it into insensitive phosphoenzyme, the splitting of which was not accelerated by potassium ion or by adenosine diphosphate. Its rate constant was 0.07 per s. In the absence of sodium ion and adenosine triphosphate, inorganic phosphate was incorporated directly into a similar insensitive phosphoenzyme. In the presence of potassium ion or rubidium ion, inorganic phosphate was incorporated into a potassium-complexed or rubidium-complexed phosphoenzyme which exchanged 32-P with inorganic phosphate completely in less than 3 s. Incorporation of inorganic phosphate into a complex of the enzyme with the inhibitor, ouabain, is already described in the literature. Its rate constant was about 0.02 per s. Thus there appear to be at least four reactive states of the phosphoenzyme which equilibrate measurably with inorganic phosphate, namely, potassium-sensitive phosphoenzyme, potassium-complexed phosphoenzyme, insensitive phosphoenzyme, and ouabain phosphoenzyme. Two of these reactive states are functional intermediates in native sodium and potassium ion transport adenosine triphosphatase. The results are compatible with control of the reactivity of the active site by conformational changes in the surrounding active center and with regulation of the energy level of the phosphate group according to the kind of monovalent cation bound to the enzyme.
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PMID:Phosphorylation by inorganic phosphate of sodium plus potassium ion transport adenosine triphosphatase. Four reactive states. 12 73

Vasodilator responses to acute intra-arterial infusions of K+ are attenuated in dogs with chronic one-kidney perinephritic hypertension in rats with chronic two-kidney Goldblatt hypertension, and in men with essential hypertension. There is evidence that K+ evokes vasodilation by stimulating vascular smooth muscle membrane Na+-K+-activated adenosine triphosphatase, thereby increasing activity of the cellular Na+-K+ electrogenic pump. We therefore proposed that there may be an underlying decrease in the operation of this pump in vascular smooth muscle of hypertensives. The operation of the cellular Na+-K+ pump may be estimated by measurement of rubidium uptake. Thus, so further investigate our hypothesis, we measured 86Rb uptake in small mesenteric arteries and splanchnic veins from 12 dogs with chronic uncomplicated one-kidney perinephritic hypertension and from 12 normotensive control dogs. Vessels were excised under thiamylal anesthesia and incubated in cold medium (plasma or Krebs-Henseleit solution) for sodium loading and then the velocity of 86Rb uptake was estimated in the absence of or in the presence of ouabain, a specific inhibitor of the Na+-K+ pump. In neither arteries nor veins was there evidence for differences between hypertensives and normotensives in the ouabain-insensitive uptake of 86Rb. In contrast, the ouabain-sensitive 86Rb uptake was depressed by 42% in arteries (P less than 0.05) and by 49% in veins (P less than 0.01) from hypertensive dogs, if incubated in the dog's own plasma. These results indicate that the activity of a ouabain-sensitive Na+-K+ pump may be depressed in vascular tissue from dogs with chronic one-kidney perinephritic hypertension. Because the Na+-K+ pump in vascular smooth muscle is probably electrogenic, such an abnormality, by partially depolarizing the muscle cell membrane, would help to account for the elevated vascular resistance found in these dogs.
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PMID:Depressed function of a ouabain-sensitive sodium-potassium pump in blood vessels from renal hypertensive dogs. 13 55

The addition of bacteriophage T5 to anaerobic, fermenting cells of Escherichia coli B or K-12 in the presence of 8-anilino-1-naphthalene sulfonate (ANS), N-phenylnaphthyl-1-amine (NPN), or dansyl ethylamine causes the fluorescence of these probes to rise in two steps, the first occurring immediately upon addition, the second delayed by 6 min. The conditions necessary for observing this phenomenon are defined (cell density, probe concentration, substrate, absence of an electron acceptor, multiplicity of infection, growth, and harvesting conditions). The magnitudes of the first and second steps in fluorescence are dependent upon the multiplicity of infection; the timing of the steps is not. The first step correlates with a breakdown in the potassium or rubidium permeability barrier of the cells, and it occurs either aerobically or anaerobically, with fermentable or nonfermentable substrates. The second step occurs only with cells that are without an available electron acceptor, are fermenting, and which have a functional membrane-bound, Ca2+-dependent adenosine triphosphatase (ATPase). The results are consistent with disturbance of energization of the cell membrane by the membrane-bound ATPase at the time of the second step in fluorescence. No changes in the intracellular level of adenosine 5'-triphosphate (ATP) was seen, whereas the extracellular level increased sharply, starting 3--6 min after phage addition. The quantity of ATP found in the medium by 30 min after infection amounted to about four times the amount present inside the cells at the time of infection. The quantity and rate of efflux of ATP was similar under aerobic and anaerobic conditions.
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PMID:Relationship between steps in 8-anilino-1-naphthalene sulfonate (ANS) fluorescence and changes in the energized membrane state and in intracellular and extracellular adenosine 5'-triphosphate (ATP) levels following bacteriophage T5 infection of Escherichia coli. 15 81

Ultrafiltrate obtained by hemodialysis of patients with uremia who were not taking cardiac glycosides was used as a source of Na, K adenosine triphosphatase inhibitor for purification and further study. Inhibitory activity was measured by a linked-enzyme assay and by effect on rubidium 86 uptake in guinea pig aortic strips. Two approaches were used in purification: dialysis with a 500 dalton membrane followed by gel filtration with Sephadex G-25, and removal of protein by acidification and boiling followed by Sephadex G-10. The first procedure failed to separate the inhibitor from the salt fraction, whereas the second separated the inhibitor from the salt peak but resulted in partial coelution of the inhibitor with endogenous pyruvate, which interferes with the linked-enzyme assay. Pooled, concentrated G-10 elution fractions from the early part of the inhibitor peak, which were free of pyruvate, produced a dose-response relationship by enzymatic assay that was close to parallel with that for ouabain. Like ouabain, these fractions also inhibited 86Rb uptake in guinea pig aorta. Despite these properties, our previous work has demonstrated that the inhibitor, unlike some other ouabain-like or digitalis-like substances obtained from blood or urine, has no apparent role in body fluid homeostasis.
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PMID:An Na, K ATPase inhibitor from ultrafiltrate obtained by hemodialysis of patients with uremia. 132 35

The sodium- and potassium-dependent adenosine triphosphatase (Na+,K(+)-ATPase) maintains the transmembrane Na+ gradient to which is coupled all active cellular transport systems. The R and S alleles of the gene encoding the Na+,K(+)-ATPase alpha 1 subunit isoform were identified in Dahl salt-resistant (DR) and Dahl salt-sensitive (DS) rats, respectively. Characterization of the S allele-specific Na+,K(+)-ATPase alpha 1 complementary DNA identified a leucine substitution of glutamine at position 276. This mutation alters the hydropathy profile of a region in proximity to T3(Na), the trypsin-sensitive site that is only detected in the presence of Na+. This mutation causes a decrease in the rubidium-86 influx of S allele-specific sodium pumps, thus marking a domain in the Na+,K(+)-ATPase alpha subunit important for K+ transport, and supporting the hypothesis of a putative role of these pumps in hypertension.
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PMID:Alteration of alpha 1 Na+,K(+)-ATPase 86Rb+ influx by a single amino acid substitution. 197 5

1. We have used n.m.r. spectroscopy to measure rubidium concentrations in the skeletal muscle of live intact rats. Using a 1.9 T superconducting magnet and an ear-phone coil tuned to both protons (1H) and rubidium (87Rb), it was possible to make measurements of both tissue rubidium content and water content, and from these measurements to obtain the rubidium concentration. 2. The n.m.r. estimate of rubidium concentration in muscle in vivo was found to be a constant 31% (SEM 4%) of that estimated by flame atomic absorption spectroscopy in an extract of excised muscle. This is close to the predicted theoretical n.m.r. visibility of 33%. The visibility was constant for muscle rubidium concentrations ranging between 10 and 34 mmol/l. 3. Rubidium concentration measurement by this method is unaffected by variations in sample geometry, sample volume, tissue conductivity, coil tuning and amplifier gain. 4. By using this method to measure changes in tissue rubidium concentration with time in the same animal, it should now be possible to assess the activity of ion transport systems, such as sodium- and potassium-activated adenosine triphosphatase in vivo, by measuring the rates of change of tissue rubidium concentrations during the administration of rubidium salts. 5. This method could also be used to measure the absolute concentration of any n.m.r.-visible nucleus and could be applied to man.
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PMID:A non-invasive method of measuring concentrations of rubidium in rat skeletal muscle in vivo by 87Rb nuclear magnetic resonance spectroscopy: implications for the measurement of cation transport activity in vivo. 215 50

Accumulating experimental evidence suggests that natriuresis in response to intravascular volume expansion is promoted by an endogenous regulator of Na+,K+-adenosine triphosphatase (ATPase). Efforts to purify this substance by a number of laboratories have as yet been unsuccessful. The properties of partially purified inhibitors from plasma, urine, and tissue often fail to possess the characteristics thought to be consistent with those of a physiological regulator. These include potency (Ki of approximately 1 nM), reversibility of inhibition, specificity for Na+,K+-ATPase, and responsiveness to relevant physiological stimuli. Two rather different candidate substances, extracted from urine and hypothalamus, have been purified to a high degree. Neither is a peptide, and both are of low molecular weight and resistant to acid hydrolysis. The substance from urine is rather nonpolar and interacts with digoxin-specific antibodies, while that from hypothalamus is polar and does not appear to share epitopes with the cardiac glycosides. On the serosal surface of the toad urinary bladder, the hypothalamic substance causes a reversible inhibition of Na+ transport, inhibits rubidium uptake in red blood cells by acting on the membrane's exterior surface, inhibits binding of ouabain to purified Na+,K+-ATPase, and reversibly inhibits hydrolysis of adenosine 5'-triphosphate by the enzyme with a Ki of 1.4 nM. The hypothalamic inhibitor may be differentiated from ouabain by their respective ionic requirements for optimal inhibition of enzymatic activity, and although both ouabain and the hypothalamic inhibitor fix Na+,K+-ATPase in its E2 conformation, the hypothalamic inhibitor does not promote phosphorylation of the enzyme by inorganic phosphate in the presence of Mg2+. Ionic requirements for inhibition also differentiate the hypothalamic inhibitor from vanadate ion, as does the inhibitor's activity in the presence of norepinephrine. Further enzymological and physiological studies will be facilitated by structural characterizations of the inhibitory substances and by the availability of a method to measure their concentrations in physiological fluids.
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PMID:The search for a hypothalamic Na+,K+-ATPase inhibitor. 243 55

1. We have measured cation transport in vivo in seven healthy volunteers under control conditions and after they had taken lithium carbonate for 21 days in doses which maintained the serum lithium concentration in the range 0.6-0.8 mmol/l. 2. We have measured cation transport in vivo after the administration of an oral load of rubidium chloride, and have found that, although intra-erythrocytic concentrations of rubidium were significantly lower 1 h after the administration of rubidium when the subjects were taking lithium, there was a significant increase in the rate of uptake of rubidium into the erythrocytes over the subsequent period of the test, suggesting a direct stimulation of sodium, potassium-activated adenosine triphosphatase by lithium. 3. Lithium administration did not affect the plasma concentration versus time profile of rubidium after the rubidium load, implying that the lithium-stimulated uptake of rubidium which occurs in erythrocytes does not necessarily occur in other cell types. 4. These results suggest that previous studies of cation transport using peripheral cells and assay systems in vitro do not necessarily reflect changes in cation transport in vivo in excitable tissues.
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PMID:Measurement of cation transport in vivo in healthy volunteers after the oral administration of lithium carbonate. 254 Sep 32

These studies were designed to investigate whether the antihypertensive effects of high potassium or low sodium diets are related to changes in vascular Na+,K+-adenosine triphosphatase (ATPase) activity. Vascular Na+,K+-ATPase was measured as ouabain-sensitive rubidium uptake in aorta incubated in buffer or plasma from spontaneously hypertensive rats (SHR) fed either a high potassium, a low sodium, or a normal diet for 2 weeks. The high potassium diet significantly increased Na+,K+-ATPase activity, whereas the low sodium diet significantly decreased activity. There was no evidence of a ouabainlike factor in plasma. The increased pump activity on the high potassium diet appeared to be due to an increase in maximum activity (Vmax) of the enzyme, rather than to an increased affinity for potassium. Potentially, an increase in Na+,K+-ATPase activity could contribute to the antihypertensive effect of potassium by hyperpolarizing the cell membrane. The decrease in vascular Na+,K+-ATPase activity on a low sodium diet probably is unrelated to its depressor effect, but it may be a homeostatic mechanism for maintaining sodium balance in the animal.
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PMID:Effects of high potassium or low sodium diet on vascular Na+,K+-ATPase activity and blood pressure in young spontaneously hypertensive rats. 295 81


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