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)

Vitreoscilla is a Gram-negative bacterium with unique respiratory physiology in which Na+ was implicated as a coupling cation for the generation of a transmembrane electrical gradient (delta psi). Thus, cells respiring in the presence of 110 mM Na+ generated a delta psi of -142 mV compared to only -42 and -56 mV for Li+ and choline, respectively, and even the -42 and -56 mV were insensitive to the protonophore 3,5-di-tert-butyl-4-hydroxybenzaldehyde (DTHB). The kinetics of delta psi formation and collapse correlated well with the kinetics of Na+ fluxes but not with those of H+ fluxes. Cyanide inhibited respiration, Na+ extrusion, and delta psi formation 81% or more, indicating that delta psi formation and Na+ extrusion were coupled to respiration. Experiments were performed to distinguish among three possible transport systems for this coupling: (1) a Na(+)-transporting ATPase; (2) an electrogenic Na+/H+ antiport system; (3) a primary Na+ pump directly driven by the free energy of electron transport. DCCD and arsenate decreased cellular ATP up to 86% but had no effect on delta psi, evidence against a Na(+)-transporting ATPase. Low concentrations of DTHB had no effect on delta psi; high concentrations transiently collapsed delta psi, but led to a stimulation of Na+ extrusion, the opposite of that expected for a Na+/H+ antiport system. Potassium ion, which collapses delta psi, also stimulated Na+ extrusion. The experimental evidence is against Na+ extrusion by mechanisms 1 and 2 and supports the existence of a respiratory-driven primary Na+ pump for generating delta psi in Vitreoscilla.
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PMID:Respiratory-driven Na+ electrical potential in the bacterium Vitreoscilla. 237 55

An ATP-dependent calcium transport component from rat liver plasma membranes was solubilized by cholate and reconstituted into egg lecithin vesicles by a cholate dialysis procedure. The uptake of Ca2+ into the reconstituted vesicles was ATP-dependent and the trapped Ca2+ could be released by A23187. Nucleotides, including ADP, UTP, GTP, CTP, GDP, AMP, and adenyl-5'-yl beta, gamma-imidophosphate, and p-nitrophenylphosphate did not substitute for ATP. The concentration of ATP required for half-maximal stimulation of Ca2+ uptake into the reconstituted vesicles was 6.2 microM. Magnesium was required for calcium uptake. Inhibitors of mitochondrial calcium-sequestering activities, i.e. oligomycin, sodium azide, ruthenium red, carbonyl cyanide p-trifluoromethoxyphenylhydrazone, and valinomycin did not affect the uptake of Ca2+ into the vesicles. In addition, strophanthidin and p-chloromercuribenzoate did not affect the transport. Calcium transport, however, was inhibited by vanadate in a concentration-dependent fashion with a K0.5 of 10 microM. A calcium-stimulated, vanadate-inhibitable phosphoprotein was demonstrated in the reconstituted vesicles with an apparent molecular weight of 118,000 +/- 1,300. These properties of Ca2+ transport by vesicles reconstituted from liver plasma membranes suggest that this ATP-dependent Ca2+ transport component is different from the high affinity (Ca2+-Mg2+)-ATPase found in the same membrane preparation (Lotersztajn, S., Hanoune, J. and Pecker, F. (1981) J. Biol. Chem. 256, 11209-11215; Lin, S.-H., and Fain, J.N. (1984) J. Biol. Chem. 259, 3016-3020). When the entire reconstituted vesicle population was treated with ATP and 45Ca in a buffer containing oxalate, the vesicles with Ca2+ transport activity could be separated from other vesicles by centrifugation in a density gradient and the ATP-dependent Ca2+ transport component was purified approximately 9-fold. This indicates that transport-specific fractionation may be used to isolate the ATP-dependent Ca2+ transport component from liver plasma membrane.
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PMID:Novel ATP-dependent calcium transport component from rat liver plasma membranes. The transporter and the previously reported (Ca2+-Mg2+)-ATPase are different proteins. 240 77

Respiration, membrane potential generation and motility of the marine alkalotolerant Vibrio alginolyticus were studied. Subbacterial vesicles competent in NADH oxidation and delta psi generation were obtained. The rate of NADH oxidation by the vesicles was stimulated by Na+ in a fashion specifically sensitive to submicromolar HQNO (2-heptyl-4-hydroxyquinoline N-oxide) concentrations. The same amounts of HQNO completely suppressed the delta psi generation. Delta psi was also inhibited by cyanide, gramicidin D and by CCCP + monensin. CCCP (carbonyl cyanide m-chlorophenylhydrazone) added without monensin exerted a much weaker effect on delta psi. Na+ was required to couple NADH oxidation with delta psi generation. These findings are in agreement with the data of Tokuda and Unemoto on Na+-motive NADH oxidase in V. alginolyticus. Motility of V. alginolyticus cells was shown to be (i) Na+-dependent, (ii) sensitive to CCCP + monensin combination, whereas CCCP and monensin, added separately, failed to paralyze the cells, (iii) sensitive to combined treatment by HQNO, cyanide or anaerobiosis and arsenate, whereas inhibition of respiration without arsenate resulted only in a partial suppression of motility. Artificially imposed delta pNa, i.e., addition of NaCl to the K+ -loaded cells paralyzed by HQNO + arsenate, was shown to initiate motility which persisted for several minutes. Monensin completely abolished the NaCl effect. Under the same conditions, respiration-supported motility was only slightly lowered by monensin. The artificially-imposed delta pH, i.e., acidification of the medium from pH 8.6 to 6.5 failed to activate motility. It is concluded that delta mu Na+ produced by (i) the respiratory chain and (ii) an arsenate-sensitive anaerobic mechanism (presumably by glycolysis + Na+ ATPase) can be consumed by an Na+ -motor responsible for motility of V. alginolyticus.
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PMID:The sodium cycle. I. Na+-dependent motility and modes of membrane energization in the marine alkalotolerant vibrio Alginolyticus. 242 48

Proton transport catalyzed by the sodium pump was demonstrated using proteoliposomes reconstituted with purified pig kidney Na+,K+-ATPase. Intravesicular pH was monitored with fluorescence from fluorescein isothiocyanate dextran introduced into the vesicles. An ATP-induced ouabain-sensitive acidification of the intravesicular medium was observed, when the vesicles were incubated with ATP and without Na+. The ATP-induced acidification was blocked by either extravesicular Na+ or pretreatment of the enzyme with ouabain before reconstitution. Protonophores, X-537A or carbonyl cyanide m-chlorophenylhydrazone, abolished the intravesicular acidification. The acidification was not inhibited by 3 mM tetra-n-butylammonium. The initial rate of the H+ uptake was increased with a decrease in pH of the extravesicular medium, and the maximum rate was obtained at pH 5.5-5.6. It is concluded that H+ can be transported in place of Na+ by the sodium pump.
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PMID:ATP-dependent proton uptake by proteoliposomes reconstituted with purified Na+,K+-ATPase. 242 23

Relationships between the Na+ dependent amino acid uptake displayed by fertilized sea urchin eggs and the electrochemical gradient of Na+ was investigated. The time course of Na+ content and valine or alanine uptake was simultaneously monitored in Na+ loaded eggs [by fertilization in K+-free artificial sea water (OK-ASW), or by using monensin, antimycin, cyanide, or ciguatoxin]. Our results demonstrate that the uphill amino acid uptake follows the "Na+ gradient hypothesis." Subsequent fertilization of eggs Na+ depleted by ammonia for 40 min stimulates to a great extent the development of amino acid uptake as compared with controls eggs. By using simultaneous change of external and intracellular Na+ concentration, we studied the specific role of this ion. An increase in internal Na+ inhibits the uptake through trans inhibitory action while an increase in external Na+ stimulates the efficiency of the uptake system. In eggs fertilized since 30 min, hyperpolarization obtained in K+-free ASW stimulates amino acid uptake while depolarization (transfer from K+ free ASW to ASW) inhibits it. This potential-dependent effect developed after fertilization with a time course similar to that the establishment of K+ conductance described by R. A. Steinhardt, L. Lundin, and D. Mazia (1971, Proc. Natl. Acad. Sci. USA 68, 2426-2430). In conclusion, our results point out that slight modulations in the activity of the Na+ pump can widely affect the amino acid uptake, suggesting that activation of Na+/K+ ATPase has a key role in the stimulation of amino acid transport.
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PMID:Regulatory and energetic role of Na+ in amino acid uptake by fertilized sea urchin eggs. 242 81

Fluorescein isothiocyanate-conjugated dextran (FITC-dextran) is internalized by endocytosis into the lysosome-like vacuoles of Saccharomyces cerevisiae (Makarow, M., 1985, EMBO (Eur. Mol. Biol. Organ.) J. 4:1861-1866). Here we show that under energy depletion conditions FITC-dextran accumulated in a cytoplasmic compartment, from which it could be chased to the vacuole when the energy block was removed. The internal pH of the intermediate compartment under energy depletion was determined by fluorometry to be 5.8. The pH could be raised by the lysosomotropic agent ammonium chloride, the protonophore carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone (CCCP) and the ATPase inhibitors dicyclohexylcarbodiimide (DCCD) and sodium vanadate. The pH of the vacuole was found to be 6.5. It was raised by ammonium chloride, CCCP, and DCCD, but not with sodium vanadate. Efrapeptin had no effect on the internal pH of either compartment. By dissecting the endocytic pathway, two portions of the route leading to the vacuole could be studied separately. The internalization of FITC-dextran from the extracellular fluid to the intermediate compartment followed linear kinetics, was independent of energy, and occurred at temperatures of between 15 degrees and 37 degrees C. Transfer of the marker from the intermediate compartment to the vacuole required energy, took place at temperatures between 19 degrees and 37 degrees C, and had a half-time of 7 min at 37 degrees C. Transport of the marker from the exterior of the cell to the vacuole did not require acidic pH values in the intermediate compartment or the vacuole. We suggest that the cytoplasmic compartment revealed by FITC-dextran, under energy depletion, represents the equivalent of the endosomes of mammalian cells.
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PMID:Transport of a fluorescent macromolecule via endosomes to the vacuole in Saccharomyces cerevisiae. 243 74

Recently a series of fluorescent calcium indicator dyes have been developed for measurement of free intracellular calcium in eukaryotic cells. Here we report the use of one such dye, fura-2, for the study of intracellular calcium levels in the prokaryote Escherichia coli. Cells of E. coli were loaded with the membrane-permeable acetoxymethyl ester of fura-2, which was cleaved intracellularly to give the free pentaacid. The concentration of free [Ca2+]i in unstarved cells was maintained at 90 +/- 10 nM, irrespective of the Ca2+ concentration in the extracellular medium. Cells of a strain lacking the H+-translocating ATPase were depleted of endogenous energy reserves and loaded with calcium. In this strain oxidative phosphorylation is uncoupled, so ATP is not produced by respiration. In starved cells [Ca2+]i varied from 0.2 to 0.7 microM when the loading Ca2+ concentration varied from 10 microM to 10 mM. Addition of glucose lowered the Ca2+ levels to 90 nM. Addition of respiratory substrates as energy donors produced cyanide-sensitive efflux. Total cell Ca2+ increased in parallel to the extracellular calcium, but the pool of free calcium did not equilibrate with the total cellular pool. These results demonstrate that 1) the pool of total Ca2+ in the bacterial cell is large and responds to extracellular calcium, 2) the free [Ca2+]i is independent of extracellular calcium, and 3) energy in the form of a proton motive force is required for maintenance of the free intracellular pool of calcium.
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PMID:Maintenance of intracellular calcium in Escherichia coli. 244 65

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

An endosomal fraction isolated from rabbit renal cortex by a novel, fast, and simple procedure was enriched in ATP-dependent H+ pumping that was oligomycin insensitive but was inhibited by dicyclohexylcarbodiimide (DCCD), N-ethylmaleimide (NEM), Zn2+, Hg2+, diethylstilbestrol, mersalyl, and 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole. No substantial Na+-H+ exchange was detected. Electrogenicity of the pump was demonstrated using [14C]-SCN-. In addition, these membranes featured ATP-dependent Cl- flux. The ATP-driven H+ pumping had an absolute requirement for Cl-: an inside-negative membrane potential was not a substitute for Cl-. The protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone inhibited ATP-driven Cl- uptake but no inhibition was observed with nigericin. Finally, both ATP-driven H+ pumping and ATP-dependent Cl- flux were inhibited by Cl(-)-channel inhibitors. Part, or all, of the absolute dependence on Cl- may derive from a Cl- channel, the function of which is intimately related to H+ pumping by the ATPase. Flux through this Cl- channel may be regulated by one or more factors, including ATP, membrane potential, and pH.
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PMID:Cl(-)-dependent ATP-driven H+ transport in rabbit renal cortical endosomes. 246 Oct 97

Uptake of 35S-labelled sulfate was studied with a new isolate of Desulfovibrio desulfuricans, strain CSN. Micromolar additions of sulfate (1-10 microM or nmol/mg protein) to cell suspensions incubated in 150 mM KCl at -1 degrees C were almost completely taken up and accumulated about 5,000-fold. Accumulation was not influenced by incubation in NaCl instead of KCl, by acidic pH (5.5) or by incubation under air for 10 min. In alkaline milieu (pH 8.5), after prolonged contact with air (2 h), or after growth with excess sulfate or thiosulfate as electron acceptor, the amount taken up was diminished approximately by half. Pasteurization inhibited sulfate uptake completely. With increasing concentrations of added sulfate (0.1 to 2.5 mM) the intracellular concentration increased only slowly up to 25 mM, and the accumulation factor decreased down to 8. Sulfate transport was reversible. Accumulated sulfate was rapidly lost from the cells after addition of excess non-labelled sulfate or after addition of the uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP). The ATPase inhibitor dicyclohexylcarbodiimide (DCCD) specifically inhibited sulfate reduction but had no immediate influence on sulfate accumulation. Addition of the phosphate analogue arsenate (5 mM) was without effect. These results were not in favour of an ATP-dependent transport system. The K+-H+-antiporter nigericin (in 150 mM KCl) and the Na+-H+-antiporter monensin (in 150 mM NaCl) caused partial inhibition of sulfate accumulation, whereas the K+-transporter valinomycin (in 150 mM KCl) and the Na+-H+ exchange inhibitor amiloride (2 mM) were without effect.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of sulfate transport in Desulfovibrio desulfuricans. 247 99


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