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)

Lysosomes (tritosomes) were purified from the livers of rats injected with Triton WR 1339. The lysosomes developed an Mg2+-ATP-dependent pH gradient as measured by Acridine orange accumulation. H+ transport was supported by chloride, but not sulfate, and was independent of the cation used. H+ transport and Mg2+-stimulated ATPase was inhibited by diethylstilbesterol (K0.5 = 2 microM). N-Ethylmaleimide inhibited H+ transport (K0.5 = 30 microM). At low concentrations of N-ethylmaleimide, ATP partially protected H+ transport from inhibition with N-ethylmaleimide. Photolysis with 8-azido-ATP inhibited H+ transport and Mg2+-stimulated ATPase activity. Under these same conditions, 8-azido-[alpha-32P]ATP reacted with a number of polypeptides of the intact lysosome and lysosomal membranes. Pump-dependent potentials were measured using the fluorescent potential-sensitive dye, DiSC3(5) (3,3'-dipropylthiocarbocyanine) and ATP-dependent potential generation was inhibited by diethylstilbesterol. Chloride, but not sulfate reduced the magnitude of the ATP-dependent membrane potential, as measured using merocyanine 540. The chloride conductance, independent of ATP, was of sufficient magnitude to generate a H+ gradient driven by external chloride in the presence of tetrachlorosalicylanilide. In Cl- free media, ATP-dependent H+ transport was restored to control levels by outwardly directed K+ gradients in the presence of valinomycin. The role of cell Cl- is to provide the necessary conductance for supporting lysosomal acidification by the electrogenic proton pump.
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PMID:The lysosomal H+ pump: 8-azido-ATP inhibition and the role of chloride in H+ transport. 295 91

C. elegans contains a microtubule binding protein that resembles both dynein and kinesin. This protein has a MgATPase activity and copurifies on both sucrose gradients and DEAE Sephadex columns with a polypeptide of Mr approximately 400 kd. The ATPase activity is 50% inhibited by 10 microM vanadate, 1 mM N-ethyl maleimide, or 5 mM AMP-PNP; it is enhanced 50% by 0.2% Triton. The 400 kd polypeptide is cleaved at a single site by ultraviolet light in the presence of ATP and vanadate. In these ways, the protein resembles dynein. The protein also promotes ATP-dependent translocation of microtubules or axonemes, "plus" ends trailing. This property is kinesin-like; however, the motility is blocked by 5 microM vanadate, 1 mM N-ethyl maleimide, 0.5 mM ATP-gamma-S, or by ATP-vanadate-UV cleavage of the 400 kd polypeptide, characteristics that differ from kinesin. We propose that this protein is a novel microtubule translocator.
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PMID:Identification of a microtubule-based cytoplasmic motor in the nematode C. elegans. 295 72

The effects of some aromatic hydrocarbons, aliphatic chlorinated hydrocarbons, and alcohols on adenosine triphosphatase (ATPase) activity in human erythrocyte ghost membrane were studied in vitro. Both aromatic and chlorinated aliphatic hydrocarbons inhibited this activity dose-dependently, the inhibition of total ATPase activity being clearer than that of magnesium-activated ATPase. Of the alcohols studied, methanol had no effect on the ATPase activity, but ethanol, propranolol, and butanol were slightly enzyme-activating at high concentrations. The enzyme-inhibiting potency of organic solvents was generally related to their lipid solubilities, but 1,1,2,2-tetrachloroethane was a potent enzyme inhibitor despite its low lipid solubility. This findings indicates that, eg, the molecular structure of solvents may modulate their enzyme inhibition. In the presence of Triton-X-100, toluene did not cause any changes in the activity of total ATPase, and the combined effect of the two compounds was slight. Triton-X-100 also caused a significant solubilization of membrane proteins although even the highest toluene concentrations did not. These results show that organic solvents may cause their membrane effects by acting directly on membrane-bound integral proteins such as ATPase. This action is not only dependent on the lipid solubility of the compounds, but also on their molecular structure.
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PMID:Effects of industrial organic solvents on human erythrocyte membrane adenosine triphosphatase activities in vitro. 296 75

The effects of four Ca2+ binding protein modulators (bepridil, perhexiline, calmidazolium and trifluoperazine) on cardiac myofibrillar ATPase activity in Triton-purified myofibrils prepared from normal dogs, normal hamsters and age/sex (male, 16-20 weeks)-matched myopathic hamsters (BIO 14.6) have been quantitated. When compared with normal hamsters, myopathic hamster myofibrils have a markedly depressed maximum MgATPase activity (178 +/- 2 vs. 119 +/- 3 nmol/mg per min, respectively) and a slightly increased requirement of Ca2+ for half-maximal activation (ED50; 0.66 vs. 0.75 microM free Ca2+, respectively). Calmidazolium, trifluoperazine and bepridil lower the ED50 for Ca2+ in myopathic myofibrils. Moreover, bepridil and trifluoperazine increase maximum myofibrillar MgATPase activity in myopathic hamster myofibrils. In contrast, calmidazolium depresses maximum and stimulates basal MgATPase activities in myopathic and normal hamster myofibrils. Qualitatively, different effects are apparent when these agents are examined in canine myofibrils. Thus, the pharmacological effects of Ca2+ binding protein modulators on cardiac myofibrillar ATPase activity are dependent upon species and/or pathological state. It is possible to directly enhance a pathological consequence of cardiac myopathy, depression in maximum myofibrillar MgATPase activity, with pharmacological agents.
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PMID:Differential effects of pharmacological modulators of cardiac myofibrillar ATPase activity in normal and myopathic (BIO 14.6) hamsters. 296 69

A polyclonal antibody to the catalytic subunit of rat kidney Na,K-ATPase has been raised in rabbits and used to analyze the turnover of the subunit in the rat hepatoma cell line HTC. It had been shown previously (Baumann, H., and Doyle, D. (1978) J. Biol. Chem. 253, 4408-4418) that the membrane proteins of these cells displayed multicomponent turnover kinetics, the minority of the surface proteins turning over with a half-time of about 20 h and the remainder with a half-time of about 100 h. That the antibody precipitated both the alpha (catalytic) and beta (glycosylated) subunits of the Na,K-ATPase from Triton extracts of HTC cells could be demonstrated following metabolic labeling of the cells with either [3H]leucine or a mixture of [3H] mannose and [3H]fucose, but following labeling with [35S]methionine radioactivity was found only in the alpha subunit of the precipitates. Incorporation of [35S]methionine into the alpha subunit could be detected 2 min after addition of the isotope to the cell suspension. Then and at all times thereafter the label was recoverable only from the particulate fraction of a 150,000 X g 60-min centrifugation; no labeled alpha subunit was ever detected in the supernatant fraction. By quantitative densitometry of radioautographs of sodium dodecyl sulfate-polyacrylamide gels of labeled antibody precipitates, it could be shown in pulse-chase experiments that the specific activity of the alpha subunit remained unchanged for 3-4 h (transit time) after the pulse was initiated and that the activity subsequently decayed exponentially with a half-time of 18 h. In a population growing with a generation time (tG) of 33 h, this decay corresponds to a turnover rate constant of 0.49/tG. The catalytic subunit is among those membrane proteins with a rapid turnover rate.
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PMID:Turnover of the catalytic subunit of Na,K-ATPase in HTC cells. 301 30

Lateral (L) cilia of Mytilus gill are activated by serotonin which, in molluscan systems, is known to activate adenylate cyclase. Triton-extracted models of L-cells, arrested at greater than 10(-6) M Ca++, are stimulated to beat by the addition of 10(-5) M cAMP while still under Ca++ arrest conditions, suggesting that cAMP-activation is not mediated by alterations of Ca++ levels. Using isolated, permeabilized cilia, we find, independent of [Ca++], that cAMP-dependent protein phosphorylation in L-cilia occurs uniquely and reversibly on three low molecular weight polypeptides of 23,000, 18,000, and 14,000 daltons. Phosphorylation is maximal at cAMP concentrations above 0.5 microM. The phosphorylated chains partially co-extract at high salt with a 14S dynein fraction and have approximately the same molecular weights as reported for dynein light chains. Such conditions mainly extract the outer dynein arm, about 40% of the Mg++-ATPase activity, and a corresponding amount of the cAMP phosphorylated chains. However, the three polypeptides sediment together at 10-11S, clearly separable from the 14S dynein ATPase. Using a gel-overlay technique, we find that calmodulin binds to axonemal polypeptides of L-cilia with molecular weights of 18,000 and 13,000, independent of Ca++, while in mixed-population cilia, only a 12,000 dalton chain binds calmodulin, in a Ca++ dependent manner. In neither case are calmodulin binding proteins found in the high salt fraction containing the cAMP-dependent phosphorylated chains, indicating that, in spite of some similarity in molecular weight, the cAMP-phosphorylated and calmodulin binding polypeptides are different. Also, double-labelling indicates that only the 18,000 dalton chains co-migrate.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Cyclic AMP and calcium in the differential control of Mytilus gill cilia. 301 53

Transverse tubule (TT) membrane vesicles contain a very active Mg-ATPase (EC 3.6.1.3). Concanavalin A (ConA) and other lectins were found to activate the TT Mg-ATPase from chicken skeletal muscle up to 25-fold yielding specific activities greater than 800 mumol/h/mg. The sarcoplasmic reticulum Ca-ATPase and the sarcolemma Na,K-ATPase were unaffected by ConA. 125I-Labeled lectin binding to the TT membrane Mr 102,000 glycoprotein supports the contention that this protein is identical with or is intimately associated with the TT Mg-ATPase. The ATPase exhibited non-Michaelis-Menton kinetics with both apparent negative cooperativity (n = 0.723; S0.5, Mg-ATP = 14 microM) and substrate inhibition (Ki, Mg-ATP = 10.2 mM), both of which were eliminated in the presence of ConA. Under the same conditions, ConA also abolished the unusual temperature dependence and potent Triton X-100 inhibition. The similarities in ConA suppression of both Triton and substrate inhibition suggest that these ligands may be interacting through a non-catalytic site and that Triton is serving as a nucleotide-mimetic agent. The unique kinetic responses are consistent with a homotropic substrate modifier mechanism wherein the enzyme can be viewed as possessing a single catalytic and a single regulatory site on a single polypeptide chain. It is proposed that ConA interferes either with ligand interaction at a putative regulatory site or blocks communication between a regulatory site and the catalytic site. The possible nature of the regulatory site and its modulation by a ConA-like, endogenous, skeletal muscle lectin and their combined role in excitation-contraction coupling is discussed.
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PMID:Studies on the transverse tubule membrane Mg-ATPase. Lectin-induced alterations of kinetic behavior. 301 68

(Ca2+ + Mg2+)ATPase (EC 3.6.1.3) was solubilized from human erythrocyte membranes by detergent extraction with Triton N-101 (0.5 mg/mg membrane protein) and purified by calmodulin affinity chromatography. ATPase activity was assayed in mixtures of Triton N-101 and phospholipid, without reconstitution into bilayer vesicles. At low levels of phospholipid (5 micrograms/ml), the ATPase activity was highly sensitive to the detergent concentration, with maximal activity occurring at or near the critical micelle concentration of the detergent. With increased amounts of phospholipid (50 micrograms/ml), detergent concentrations greater than the critical micelle concentration were required for maximal activity. Detergent alone did not support ATPase activity. Sonicated phospholipid in the form of vesicles was equally ineffective. Activity seemed to be dependent on the presence of detergent/phospholipid mixed micelles. The acidic phospholipids, phosphatidylserine and phosphatidylinositol, as well as the commercial phospholipid preparation, Asolectin, gave activities five to eight times greater than the same amount of phosphatidylcholine. Mixtures of phosphatidylserine and phosphatidylcholine produced intermediate ATPase activities, with the maximal value dependent on the phosphatidylserine concentration. Addition of phosphatidylcholine to fixed concentrations of phosphatidylserine caused a rise in activity that was independent of the ratio of the two phospholipids or the total phospholipid concentration. Phosphatidylcholine may therefore be irreplaceable for some aspect of ATPase function. The number of phospholipid molecules present in mixed micelles at maximal ATPase activity was calculated to be near 50. This value implied that the hydrophobic surface of the ATPase molecule must be completely coated by a single layer of phospholipid molecules for maximum activity to occur.
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PMID:Phospholipid and detergent effects on (Ca2+ + Mg2+)ATPase purified from human erythrocytes. 315 27

Vesiculated fragments of chicken skeletal muscle transverse tubule (TT) membranes were analyzed for their content of loosely associated and integral membrane proteins. Of particular interest was the identification of the magnesium-stimulated ATPase (Mg-ATPase), which is characteristically located in native isolated TT vesicles of chicken skeletal muscle [R. A. Sabbadini and V. R. Okamoto (1983) Arch. Biochem. Biophys. 223, 107-119]. A number of the proteins found in vesicular TT preparations were found to be extractable by a mild Triton-X100 treatment and were identified as aldolase, enolase, creatine kinase, glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, and pyruvate kinase. Approximately 60% of TT-associated protein was extracted with Triton, resulting in a twofold enrichment of the Mg-ATPase. Concommitantly, one core integral membrane protein possessing a Mr of 102,000 was enriched, suggesting that it is responsible for the Mg-ATPase activity present in chicken skeletal muscle TT membranes.
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PMID:Characterization of transverse tubule membrane proteins: tentative identification of the Mg-ATPase. 315 29

Cilia membrane preparations from axenically grown Paramecium contain ATPase activities with distinct electrophoretic mobilities on Triton-polyacrylamide gels [M.J. Doughty and E.S. Kaneshiro (1983) J. Protozool. 30, 569-575]. Such gel analyses also show additional ATPase activity bands associated with ciliary axonemes (dyneins), cell pellicles, exocytotic trichocysts, and the external cell surface (ectoenzyme). In the present report, the in vitro properties of these activities in various cell fractions were compared. The activity in ciliary membranes was stimulated by Ca2+ greater than Mg2+, in pellicles by Ca2+ greater than Mg2+, and in trichocysts by Ca2+ = Mg2+. The ecto-ATPase was strictly Ca2+ dependent. Determination of the affinities for various phosphate-containing substrates showed that the activities in all fractions were nucleoside triphosphate phosphohydrolases. Unlike the axonemal dynein ATPases, all other fractions were vanadate- and p-chloromercuribenzoate-insensitive. Activities in all cell fractions were sensitive to ruthenium red, the ciliary membrane being the most sensitive (Ki = 4 microM). The ciliary membrane Ca2+ ATPase activity exhibited an apparent affinity for CaATP2- of 9 microM and was inhibited by other divalent cations, La3+, and phosphate, but not by ADP or AMP. The kinetic properties of the ciliary membrane Ca2+ ATPase activity in wild type and several behavioral mutants were similar except for those in the pawn mutant, d495, and the paranoiac mutant, d490, both of which had lower specific activities. These studies support the finding that the ciliary membrane ATPase activity of Paramecium is a specific Ca2+-dependent ATPase distinct from other divalent cation-dependent ATPase activities found in either the cilia or other cell surface structures.
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PMID:Divalent cation-dependent ATPase activities in ciliary membranes and other surface structures in Paramecium tetraurelia: comparative in vitro studies. 315 47


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