Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Albumin-free testis mitochondrial ATPase activity failed to be stimulated by either 2,4-dinitrophenol (DNP) or carbonyl cyanide rho-trifluoromethoxyphenylhydrazone (FCCP). DNP scarcely enhanced the state 4 respiration and mitochondria proved to be poorly coupled. When 1% bovine serum albumin was added to the isolation medium, DNP or FCCP stimulated ATPase nearly twofold and the dose-response curves for the uncouplers on the QO2 reached a plateau at five- to sixfold. The DNP coupling index (q) also showed a 30-40% improvement. A dose-response curve for oligomycin on the rate of [gamma-32P]ATP synthesis showed a stimulation of ATP synthase activity by 10-100 ng inhibitor/mg protein, suggesting a possible blockade of "open" F0 channels. In the albumin preparation oligomycin inhibited ATP synthesis in the range 10-100 ng/mg protein. Since testis ATPase is known to be loosely bound to the membrane, an effect of albumin, improving tightness in the interaction of the F1 and the F0 sectors of the ATPase, is suggested.
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PMID:The insensitivity to uncouplers of testis mitochondrial ATPase. 244 29

1. The addition of mersalyl to aged mitochondria from rat kidneys, is followed by induction of an ATP-driven Ca2+ uptake which is sensitive to Ruthenium Red. 2. This Ca2+ influx requires Mg2+, albumin, and is accomplished by membrane energization. 3. The activation of Ca2+ uptake by the mercurial in the presence of ATP can be explained if it is assumed that the inorganic phosphate generated by ATPase activity, and trapped in the matrix by the thiol reagent, provides the negative potential which results in an electrophoresis cation influx.
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PMID:Induction of mitochondrial Ca2+ uptake by mersalyl. 248 4

The total time-controlled ischemia (up to 45 min) was studied for its effect on the Na,K-ATPase activity, content of nonesterified fatty acids (NEFA) and intensity of lipid peroxidation (LP) in sarcolemmal (SL) preparations and soluble fractions (SF) from the rat and guinea-pig left ventricles. A strong correlation between Na, K-ATPase inhibition and NEFA accumulation was revealed in the SF. On the contrary, changes in the NEFA content and LP level both in SL and SF did not correlate with a decrease in the enzymic activity. Pretreatment with albumin (0.5 mg/ml) induced equally small increase both in the control and in the ischemic SL preparations. It is suggested that the Na,K-ATPase activity during a short period of myocardial ischemia (up to 45 min) may be due to the NEFA accumulation in the cytosolic and/or extracellular space, but not in SL.
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PMID:[Na,K-ATPase activity in the myocardial sarcolemma in ischemia]. 255 47

The hypothesis that fluid reabsorption from the air spaces is mediated at least in part by active transport of Na+ was investigated in six sets of experiments conducted in isolated fluid-filled rat lungs. Fluid reabsorption was monitored by following the changes in the air space concentration of labeled albumin. We found that incorporation of bicarbonate rather than a nonvolatile buffer (N-2-hydroxy-ethylpiperazine-N'-2-ethanesulfonic acid) in the air space solution more than doubled the rate of fluid reabsorption. Addition of 10(-4) M amiloride to the air space solution reduced the rate of fluid reabsorption over a 2-h experiment from 1.2 +/- 0.1 to 0.7 +/- 0.1 ml and decreased reabsorption of both labeled and unlabeled Na+ from the air spaces. To show that Na+ could be reabsorbed from the air spaces even if the concentrations of Na+ in the perfusate increased above those in the air space, mannitol (150 mM) was added to the perfusate and air space solutions and the concentrations of Na+ and Cl- were reduced to 90 and 60 mM, respectively. Mannitol diffuses across the pulmonary epithelium very slowly, and it osmotically restrained the movement of water out of the air spaces. Na+ concentrations in the perfusate increased by 10 +/- 2 mM, but concentrations in the air space remained unchanged. Despite an increasingly unfavorable concentration gradient for Na+, 0.2 mmol Na+ and 0.6 ml water were reabsorbed from the air spaces in 2 h. Ouabain (10(-4) M) did not appear to slow fluid reabsorption in the presence of mannitol, but it reduced K+ secretion into the air spaces and increased K+ appearance in the perfusate in a manner consistent with inhibition of Na+-K+-adenosinetriphosphatase at the basolateral surface of the epithelial cells. Fluid reabsorption was not altered when the lungs were exposed to a hypotonic solution (185 mM), but secretion of K+ into the air spaces was accelerated and K+ was lost from the perfusate. These experiments are consistent with active Na+ transport from the air spaces.
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PMID:New evidence for active sodium transport from fluid-filled rat lungs. 270 20

Despite multiple procedures used to isolate transverse tubule vesicles from rabbit skeletal muscle, few proteins have been identified and shown to be specific to transverse tubule vesicles. Markers for purified transverse tubules have included high affinity dihydropyridine binding, cholesterol content, Mg2+-ATPase activity, (Na+,K+)-ATPase activity, and [3H] ouabain binding. Despite these markers, few proteins from purified transverse tubules can be unequivocally identified using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In this report we have biochemically and immunologically identified rabbit albumin as a major component of purified transverse tubule membranes from rabbit skeletal muscle. Albumin composed between 5.1 and 9.8% (n = 4) of the total protein in purified transverse tubules based on scans of SDS-PAGE. Furthermore, albumin and other serum proteins are present in preparations of transverse tubules and triads but not in light sarcoplasmic reticulum. Extraction of triads with low concentrations of saponin or sodium dodecyl sulfate completely removes albumin without removing intrinsic membrane proteins. Our results suggest that albumin and other serum proteins are present in the lumen of preparations of transverse tubules and albumin may be used as a marker for the transverse tubules when analyzed on SDS gels.
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PMID:Albumin is a major protein component of transverse tubule vesicles isolated from skeletal muscle. 273 47

Affinity chromatography, using Cibacron blue F3GA bound to Sepharose 4B, and Sephadex G-150 column chromatography, permit the isolation of large quantities of non-esterified cholesterol loaded albumin from rat serum. Unlabeled cholesterol and cholesterol oxides displaced 14C-cholesterol bound to albumin in a dose-dependent manner. Binding of 14C-cholesterol to rat serum albumin in vitro follows a sigmoid curve. Ca2+ ions (up to 10 mM) inhibited the cholesterol binding to albumin in vitro. Fluorescence anisotropy of diphenyl-hexatriene (DPH) embedded in the lipid core of rat brain synaptosomal plasma membranes (SPM) increased with albumin-cholesterol incorporation and decreased in parallel to cholesterol removal. The allosteric properties of the SPM-bound (Na+ + K+)ATPase by fluoride (F-) (as reflected by changes in the Hill coefficient) were modulated by albumin-cholesterol, suggesting that the physical state of the (Na+ + K+)ATPase lipid microenvironment changed from a liquid-crystalline to gel phase. The present studies concerning albumin-cholesterol complex, its behavior and its role in the structure of biomembranes, provide important new clues to the role of this fascinating molecule in normal and pathological states.
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PMID:Effect of rat serum albumin-cholesterol on the physical properties of biomembranes. 282 3

Hypokalemia has been demonstrated to be the major side effect of gossypol administration for contraceptive purposes; however, the cellular and molecular mechanisms involved in this effect are unknown. This study investigated the effect of gossypol on the activity of (Na+ and K+)-ATPase purified from the rabbit kidney and the functions of erythrocyte membrane. Kinetic findings indicated gossypol is noncompetitive with ATP, Mg2+, Na+, and K+. On the other hand, gossypol inhibited the enzyme activity of (Na+ and K+)=ATPase, expressed the hemolysis in vitro in a concentration-dependent manner, and increased the K+ efflux of the cells. These effects were antagonized by 1-2% serum bovine albumin. These findings demonstrate that gossypol is a specific and potent membrane active agent capable of injuring the cell membrane.
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PMID:Effects of gossypol on the activity of kidney (Na+ + K+)-ATPase and the functions of erythrocyte membrane. 283 26

Exposure to CO2 acidifies the cytosol of mitochondria-rich cells in turtle bladder epithelium. The result of the decrease in pH in these, the acid-secreting cells of the epithelium, is a transient increase in cell calcium, which causes exocytosis of vesicles containing proton-translocating ATPase. Because mitochondria-rich cells have rapid luminal membrane turnover, we were able to identify single mitochondria-rich cells by their endocytosis of rhodamine-tagged albumin. Using fluorescence emission of 5,6-carboxyfluorescein at two excitation wavelengths, we measured cell pH in these identified mitochondria-rich cells and found that although the cell pH fell, it recovered within 5 min despite continuous exposure to CO2. This pH recovery also occurred at the same rate in Na+-free media. However, pH recovery did not occur when luminal pH was 5.5, a condition under which the H+-pump does not function, suggesting that recovery of cell pH is due to the luminally located H+ ATPase. Chelation of extracellular calcium by EGTA prevented the CO2-induced rise in cell calcium measured with the intracellular fluorescent dyes Quin 2 or Fura 2 and also prevented recovery of cell pH. When the change in cell calcium was buffered by loading the cells with high concentrations of Quin 2, the CO2-induced decrease in pH did not return back to basal levels. We had found previously that buffering intracellular calcium transients prevented CO2-stimulated exocytosis. Further, we show here that the increased H+ current in voltage-clamped turtle bladders, which is directly proportional to the number of H+-pump-containing vesicles that fuse with the luminal membrane, was significantly reduced in calcium-depleted bladders. These results suggest that pH regulation in these acid-secreting cells occurs by calcium-dependent exocytosis of vesicles containing proton pumps, whose subsequent turnover restores the cell pH to its initial levels.
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PMID:Regulation of cell pH by Ca+2-mediated exocytotic insertion of H+-ATPases. 287 Oct 30

It is shown that Mg2+, Ca2+-ATPase activity of plasma membrane fragments from the rat small intestine myocytes is inhibited by p-chloromercuribenzoate and dithionitrobenzoate (50 and 90%, respectively). The effect of p-chloromercuribenzoate inhibition is removed by serum albumin promoting a rise in the ATPase activity of the plasma membranes and shifting the temperature maximum point up to 32 degrees C (in the norm the maximum is observed at 36 degrees C). According to the data presented, albumin changes the composition and phase state of the lipid surrounding of the membrane enzymes.
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PMID:[Effect of n-chloromercuribenzoate and albumin on Mg2+, Ca2+-ATPase activity of plasma membranes of smooth muscle cells]. 293 80

The myotoxin from B. asper snake venom inhibited Ca-ATPase activity of rabbit sarcoplasmic reticulum after incubation in vitro. Inhibition was non-competitive and albumin enhanced the effect of the toxin. Furthermore, B. asper myotoxin hydrolyzed sarcoplasmic reticulum phospholipids and induced a dose-dependent release of horseradish peroxidase that had been trapped in sarcoplasmic reticulum vesicles. Binding studies indicated that myotoxin does not bind to any particular protein of this membrane, suggesting that the toxin might interact with phospholipids. Inhibition of Ca-ATPase is probably a consequence of an alteration in sarcoplasmic reticulum phospholipids.
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PMID:Effects of a myotoxic phospholipase A2 isolated from Bothrops asper venom on skeletal muscle sarcoplasmic reticulum. 296 9


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