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)

Uptake of 2-deoxyglucose, alpha-methylglucopyranoside, and glucose into intact cells of Brochothrix thermosphacta (formerly Microbacterium thermosphactum, ATCC 11509) was stimulated by KCN or CCCP. The glucose analogs were recovered almost totally as the sugar phosphates. Membrane vesicles were isolated from protoplasts and shown to be right side out by freeze fracturing and by using ATPase as a marker for the cytoplasmic membrane surface. Uptake of glucose into vesicles was dependent on the presence of phosphoenolpyruvate. NADH oxidation, K+ -diffusion gradients, and externally directed lactate gradients (pH greater than 7 initially) were used to generate transmembrane potentials across membrane vesicles. Above a threshold value of about -50 mV, uptake of glucose into membrane vesicles was reduced. Likewise, the maximum uptake of glucose and its two analogs into cells occurred when the protonmotive force was less than about -50 mV.
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PMID:Regulation of the glucose phosphotransferase system in Brochothrix thermosphacta by membrane energization. 299 14

Ca2+ transport across mammary-gland Golgi membranes was measured after centrifugation of the membrane vesicles through silicone oil. In the presence of 2.3 microM free Ca2+ the vesicles accumulated 5.8 nmol of Ca2+/mg of protein without added ATP, and this uptake was complete within 0.5 min. In the presence of 1 mM-ATP, Ca2+ was accumulated at a linear rate for 10 min after the precipitation of intravesicular Ca2+ with 10 mM-potassium oxalate. ATP-dependent Ca2+ uptake exhibited a Km of 0.14 microM for Ca2+ and a Vmax. of 3.1 nmol of Ca2+/min per mg of protein. Ca2+-dependent ATP hydrolysis exhibited a Km of 0.16 microM for Ca2+ and a Vmax. of 10.1 nmol of Pi/min per mg of protein. The stoichiometry between ATP-dependent Ca2+ uptake and Ca2+-stimulated ATPase varied between 0.3 and 0.7 over the range 0.03-8.6 microM-Ca2+. Both Ca2+ uptake and Ca2+-stimulated ATPase were strongly inhibited by orthovanadate, which suggests that the major mechanism by which Golgi vesicles accumulate Ca2+ is through the action of the Ca2+-stimulated ATPase. However, Ca2+ uptake was also decreased by the protonophore CCCP (carbonyl cyanide m-chlorophenylhydrazone), indicating that it may occur by other mechanisms too. The effect of CCCP may be related to the existence of transmembrane pH gradients (delta pH) in these vesicles: the addition of 30 microM-CCCP reduced delta pH from a control value of 1.06 to 0.73 pH unit. Golgi vesicles also possess a Ca2+-efflux pathway which operated at an initial rate of 0.5-0.57 nmol/min per mg of protein.
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PMID:Ca2+ transport and Ca2+-dependent ATP hydrolysis by Golgi vesicles from lactating rat mammary glands. 315 70

Purified plasma membrane vesicles from GH3 rat anterior pituitary cells exhibit a Mg2+-ATP-dependent Ca2+ transport activity. Concentrative uptake of Ca2+ is abolished by exclusion of either Mg2+ or ATP or by inclusion of the Ca2+ ionophore A23187. Furthermore, addition of A23187 to vesicles which have reached a steady state of ATP-supported Ca2+ accumulation rapidly and completely discharges accumulated cation. Ca2+ uptake is unaffected by treatment of vesicles with oligomycin, the uncoupler CCCP, or valinomycin and is greatly reduced in non-plasma membrane fractions. Likewise, Ca2+ accumulation is not stimulated by oxalate, consistent with the plasma membrane origin of this transport system. (Na+, K+)-ATPase participation in the Ca2+ transport process (i.e. via coupled Na+/Ca2+ exchange) was eliminated by omitting Na+ and including ouabain in the reaction medium. Ca2+ transport activity in GH3 vesicles has a similar pH dependence as that seen in a number of other plasma membrane systems and is inhibited by orthovanadate in the micromolar range. Inhibition is enhanced if the membranes are preincubated with vanadate for a short time. A kinetic analysis of transport indicates that the apparent Km for free Ca2+ and ATP are 0.7 and 125 microM, respectively. The average Vmax is 3.6 nmol of Ca2+/min/mg of protein at 37 degrees C. Addition of exogenous calmodulin or calmodulin antagonists had no significant effect on these kinetic properties. GH3 plasma membranes also contain a Na+/Ca2+ exchange system. The apparent Km for Ca2+ is almost 10-fold higher in this system than that for ATP-driven Ca2+ uptake. When both processes are compared under similar conditions, the Vmax of the exchanger is approximately 2-3 times that of ATP-dependent Ca2+ accumulation. Similar results are obtained when purified plasma membranes from bovine anterior pituitary glands were investigated. It is suggested that both Na+/Ca2+ exchange and the (Ca2+ + Mg2+)-ATPase are important in controlling intracellular levels of Ca2+ in anterior pituitary cells.
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PMID:Mechanisms of Ca2+ transport in plasma membrane vesicles prepared from cultured pituitary cells. II. (Ca2+ + Mg2+)-ATPase-dependent Ca2+ transport activity. 614 14

The uptake of ethidium bromide by Escherichia coli K 12 cells has been studied by using 14C-labeled ethidium and spectrofluorometry on three E. coli strains: the first one (AB1157) has an ethidium-resistant phenotype; the second one derives from the first one after a single mutation (at 10 min on the E. coli genetic map) and has an ethidium-sensitive (Ebs) phenotype; the third one is the acrA strain which appeared to have the same phenotype as the Ebs strain. When the cells are in exponential growth, no ethidium enters wild-type cells, and a very limited amount of ethidium enters Ebs and acrA cells. Massive quantities of ethidium enter AB1157, Ebs, and acrA cells treated by uncouplers and respiring Ebs cells treated by the membrane ATPase-inhibitor dicyclohexylcarbodiimide. A small amount of ethidium enters cells treated in M9 succinate medium by metabolic inhibitors such as KCN or cells starved with oxygen in the same M9 medium. The amount of ethidium and ethidium dimer retained at equilibrium by either type of cell, and by cells infected by T5 phage, as well as the kinetics of influx and efflux, has been measured under a variety of situations (membrane energized or not, and/or membrane ATPase inhibited or not). Furthermore, it was shown that ethidium binds to both RNA and DNA when it enters CCCP-treated wild-type E. coli cells, whereas it binds mainly to DNA when it enters Ebs and acrA cells in exponential growth. As it will be discussed, it is difficult to account for the EthBr uptake by invoking only membrane functions and active transport. Therefore, it is proposed that the variations of the nucleic acid accessibility in E. coli cells might play a role in the control of this uptake. Accordingly, in ethidium-sensitive cells, the mutation would have caused a significant part of the chromosomal DNA (10-20%) to become accessible to ethidium. Hansen [Hansen M. T. (1982) Mutat. Res. 106, 209-216], after a study of the photobinding of psoralen to nucleic acids in the acrA mutant, also suggested that DNA environment was modified in acrA cells.
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PMID:Effect of mutation, electric membrane potential, and metabolic inhibitors on the accessibility of nucleic acids to ethidium bromide in Escherichia coli cells. 619 94

A photoregulated reversible protein phosphorylation system controlled by the halobacterial rhodopsins was recently reported. The results presented in this paper identify the initial steps in the pathway from the absorption of light to the photoregulated protein phosphorylation and dephosphorylation reactions. Action spectrum, biochemical, and genetic analyses show that the proton pump bacteriorhodopsin mediates light-induced dephosphorylation of three photoregulated phosphoproteins. Light absorbed by bacteriorhodopsin is used to establish a proton efflux from the cells. The increase in the inwardly directed protonmotive force (pmf) from this efflux induces dephosphorylation of the three phosphoproteins, as demonstrated by the effects of the protonophore CCCP and of artificially imposed transmembrane pH gradients. Upon darkening the cells, cessation of the proton efflux through bacteriorhodopsin causes a decrease in pmf, which induces rephosphorylation of the proteins. Pmf appears to function as a regulator rather than a driving force in this system. Measurements of pmf-driven ATP synthesis in our conditions indicate the regulation of protein phosphorylation by pmf is probably not a consequence of proton flux through the H+ ATPase, a known energy coupling structure in these cells. The properties of this system may indicate the existence of a pmf detector which regulates kinase or phosphatase activity; i.e., a regulatory coupling device.
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PMID:Photosensitive phosphoproteins in Halobacteria: regulatory coupling of transmembrane proton flux and protein dephosphorylation. 627 13

The uncoupler-stimulated mitochondrial ATPase of four human tumors, mouse kidney, brain and fetal liver exhibited a characteristic behavior when preincubated with the H+-conducting uncouplers, dinitrophenol, CCCP, S-13 and gramicidin. The ATPase activity was considerably lower with preincubation than without. Preincubation with valinomycin (+ K+), on the other hand, did not result in a significant decrease of the ATPase activity. These results may be contrasted with those obtained with liver or heart mitochondria, the ATPase activity of which did not suffer any loss when preincubated with dinitrophenol. The effect of preincubation with dinitrophenol on the tumor mitochondria could not be accounted for by dinitrophenol-induced Mg2+ efflux, since the differential effects of dinitrophenol and valinomycin (+ K+) remained even when ATPase activity was determined in presence of Mg2+. Small amounts of ATP and ADP in the preincubation mixture containing dinitrophenol protected against the decay of the ATPase activity, implicating the exchangeable adenine nucleotides in the tumor mitochondria. In a model system where liver mitochondria were depleted of their adenine nucleotides, a lower ATPase activity was indeed obtained. However, direct determination of the concentrations of adenine nucleotides in dinitrophenol- and valinomycin-treated tumor mitochondria revealed only slight differences.
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PMID:Differential effects of 2,4-dinitrophenol and valinomycin (+ K+) on uncoupler-stimulated ATPase of human tumor mitochondria. 628 84

The membrane potential (Em) of normal and Plasmodium chabaudi-infected rat erythrocytes was determined from the transmembrane distributions of the lipophilic anion, thiocyanate (SCN), and cation, triphenylmethylphosphonium (TPMP). The SCN- and TPMP-measured Em of normal erythrocytes are -6.5 +/- 3 mV and -10 +/- 4 mV, respectively. The TPMP-measured Em of infected cells depended on parasite developmental stage; "late" stages (schizonts and gametocytes) were characterized by a Em = -35 mV "early stages (ring and copurifying noninfected) by a low Em (-16 mV). The SCN-determined Em of infected cells was -7 mV regardless of parasite stage. Studies with different metabolic inhibitors including antimycin A, a proton ionophore (carbonylcyanide m-chlorophenylhydrazone [CCCP] ), and a H+ -ATPase inhibitor (N,N'-dicyclohexylcarbodiimide, [DCCD] ) indicate that SCN monitors the Em across the erythrocyte membrane of infected and normal cells whereas TPMP accumulation reflects the Em across the plasma membranes of both erythrocyte and parasite. These inhibitor studies also implicated proton fluxes in Em-generation of parasitized cells. Experiments with weak acids and bases to measure intracellular pH further support this proposal. Methylamine distribution and direct pH measurement after saponin lysis of erythrocyte membranes demonstrated an acidic pH for the erythrocyte matrix of infected cells. The transmembrane distributions of weak acids (acetate and 5,5-dimethyloxazolidine-2,4-dione) indicated a DCCD-sensitive alkaline compartment. The combined results suggest that the intraerythrocyte parasite Em and delta pH are in part the consequence of an electrogenic proton pump localized to the parasite plasma membrane.
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PMID:Membrane potential of Plasmodium-infected erythrocytes. 628 30

The efflux of adenine nucleotides from three human tumor mitochondria has been investigated with mitochondria prelabeled with radioactive ATP. Uncouplers induce a large efflux of adenine nucleotides from mitochondria from human hepatoma and oat cell carcinoma while efflux from astrocytoma mitochondria is less. This efflux does not require exchangeable anions, i.e., adenine nucleotides or pyrophosphate, in the extramitochondrial medium, and is not sensitive to atractyloside. The efflux is more extensive with dinitrophenol and CCCP than with valinomycin-K+, and may account for the differential effects of the two types of uncouplers on uncoupler-stimulated ATPase of tumor mitochondria previously reported by us. Dinitrophenol and CCCP do not elicit any efflux of adenine nucleotides from normal liver mitochondria. Efflux of orthophosphate from tumor mitochondria is also greater with dinitrophenol and CCCP; however, the more interesting finding is that the concentration of orthophosphate in these mitochondria is unusually high, i.e., 10-40-times greater than the intramitochondrial phosphate concentration of liver mitochondria. Atractyloside sensitive transport of ATP and ADP in human tumor mitochondria has also been determined. Vmax values for both ADP and ATP transport are lower than those obtained with liver mitochondria, especially with ADP transport. ATP transport in tumor mitochondria is not affected by CCCP in contrast to the 4-5-fold stimulation observed in liver mitochondria.
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PMID:Characteristics of adenine nucleotide fluxes and transport in human tumor mitochondria. 632 Aug 71

We studied hepatic mitochondria to determine the effects of ethanol in vitro and of chronic ethanol consumption on the temperature dependence (10 degrees-45 degrees C) of a) substrate oxidation, and b) ATP hydrolysis, with or without CCCP. Arrhenius plots showed the characteristic breaks around 20 degrees C both for electron transport and ATP hydrolysis with high energy of activation at low temperature and low energy of activation at high temperature. Ethanol, in vitro, generally lowered the energy of activation at high temperature and shifted the break in the Arrhenius plots to lower temperatures suggesting an increase in membrane fluidity. At 40 degrees C and above ethanol accelerated electron transport and greatly stimulated ATPase activity. In mitochondria from ethanol-fed rats, Arrhenius plots showed a shift in the breaks to a higher temperature, a finding which suggests a change in membrane structure, possibly associated with decreased fluidity. This may be an adaption of the mitochondrial membranes to counter the effect of ethanol on membrane structure.
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PMID:The temperature dependence of respiration and ATPase in rat liver mitochondria is altered by ethanol. 644 40

Generation of electric (delta psi) and chemical (delta pH) components of electrochemical proton gradient delta muH+, in plasma membrane vesicles of Heracleum sosnovskyi phloem cells was investigated. ATP-dependent generation of delta psi at pH 6.0 in the presence of Mg2+ and K+ was established with the help of fluorescent probes AU+ and ANS-. Protonophore CCCP and proton ATPase inhibitor DCCD suppressed generation, whereas oligomycin, the inhibitor of mitochondrial ATPases did not affect it. Measurings of delta psi value indicated its oscillations within the limits from 10 to 60 mV. ATP-dependent generation of delta pH was established by means of fluorescent probe 9-AA. The effect was eliminated by CCCP and stimulated by K+, that may testify to the transformation of a part of delta psi into delta pH at antiport H+/K+. Existence of H+-ATPase in the plasma membranes of higher plant cells insuring generation of delta muH+ is supposed.
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PMID:[Active electrogenic transport H+ in plasma membrane vesicles of cow parsnip phloem cells]. 646 61


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