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

---

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

A vesicular microsomal fraction isolated from hog fundic mucosa demonstrates the capacity to take up equal amounts of RB+ and Cl-. The amount of the Rb+ uptake is sensitive to the extravesicular osmolarity, and rate of uptake is sensitive to temperature. 86Rb+ efflux is dependent upon the cation composition of the diluting solution. ATP, but not beta-gamma methylene ATP, induces a reversible efflux of 86Rb+ from loaded vesicles, and this is dependent upon a functional K+-ATPase. The ATP induced efflux is not affected by CCCP (carbonyl cyanide m-chlorophenylhydrazone) or TCS (tetrachlorosalicylanilide) nor by lipid soluble ions or valinomycin. Nigericin inhibits the efflux by 40%. Uptake of the lipid soluble ion 14C-SCN- has been demonstrated and is enhanced by ATP only in the presence of valinomycin. The results are consistent with a neutral or isopotential exchange of H+ for Rb+ mediated by K+-ATPase.
...
PMID:Cation transport by gastric H+:K+ ATPase. 1 7

Bioflavonoids are potent inhibitors of lactate transport in Ehrlich ascites tumor cells. The most effective bioflavonoids have four to five hydroxyl groups. Sugar substitution at carbon three, or reduction of the double bond between carbons two and three, decreases their inhibitory activity. Quercetin, the most extensively studied of these compounds, inhibits lactate efflux by 50% at 0.1 micrograms/mg of protein. On addition of quercetin to glycolyzing Ehrlich ascites tumor cells, lactate accumulates inside the cell and the intracellular pH drops. Total lactate production is also inhibited. Nigericin prevents the internal acidification that occurs in the presence of quercetin and also reduces the inhibition of glycolysis. Thus, it appears that inhibition of lactate efflux can affect glycolysis through a lowering of the intracellular pH. The inhibitory effect of quercetin on glycolysis can be explained by its effect on lactate efflux and its previously reported effect on the Na+--K+ ATPase [Suolinna, E.--M., et al. (1974) J. Natl. Cancer Inst. 53, 1515].
...
PMID:Inhibition of lactate transport and glycolysis in Ehrlich ascites tumor cells by bioflavonoids. 3 32

Ca2+ uptake into Ehrlich ascites tumor cells was studied at 0 degrees C in the presence of mitochondrial inhibitors, conditions that minimized complications caused by sequestration of Ca2+ into organelles or by excretion. Under these conditions Ruthenium Red inhibited Ca2+ uptake, but other previously implicated ions, such as Pi or Mg2+, had no effect. Valinomycin either inhibited or slightly stimulated Ca2+ uptake depending on the presence of excess K+ on the outside or inside of the cell, respectively. Nigericin inhibited Ca2+ transport. Based on these data we propose an electrogenic uptake of Ca2+, possibly via a Ca2+/H+ antiport mechanism. The observation that glucose inhibited Ca2+ uptake suggested that in Ehrlich ascites tumor cells an energy-driven Ca2+ expulsion mechanism is operative, similar to that in erythrocytes. Plasma membrane preparations of ascites tumor cells were found to contain a Ca2+-dependent ATPase. These preparations, when incorporated into liposomes in an inside-out orientation, catalyzed an ATP-dependent uptake of Ca2+.
...
PMID:Ca2+ translocation in Ehrlich ascites tumor cells. 15 90

1. The basal decay of the carotenoid shift of chromatophores from photosynthetic bacteria following short flash excitation is approximately biphasic. The decay indicates the dissipation of the transmembrane electrical potential. 2. The H+ efflux following rapid H+ binding after a flash, measured from the colour change of added cresol red, shows very similar kinetics to the carotenoid shift decay suggesting that the dissipation of the electric potential decay is a consequence of the H+ efflux. 3. The electric potential decay is stimulated when the chromatophore suspension is supplemented with ADP and Pi (in either the presence or absence of antimycin A). 4. The stimulated electric potential decay by ADP and Pi has a similar pH dependence to that of phosphorylation in continuous light. 5. The stimulation of the electric potential decay by ADP and Pi is reversed, by aurovertin, an antibiotic which inhibits phosphorylation. 6. The stimulation of the electric potential decay by ADP+Pi is also reversed by the inhibitors oligomycin and venturicidin. These inhibitors, but not aurovertin, also inhibit the fast phase of the decay under non-phosphorylating conditions. 7. Valinomycin accelerates the overall rate of decay of the electric potential, inhibits the ADP and Pi stimulated electric potential decay, and inhibits the flash-induced phosphorylation. The decay rate of the H+ efflux however, is slower in the presence of this ionophore. 8. Nigericin-type ionophores accelerate the overall decay rate of the H+ efflux and inhibit the ADP and Pi stimulated electric potential decay. The basal rate of the electric potential decay is unaffected by treatment with these ionophores. 9. When a coupling factor associated with the chromatophore ATPase is removed from the membrane, both the stimulation of the electric potential decay by ADP and Pi and ADP phosphorylation are inhibtied. Both reactions are completely restored after reconstitution with the crude coupling factor extract. The basal electric potential decay rate is not affected by the removal of coupling factor.
...
PMID:Electrical potential changes, H+ translocation and phosphorylation induced by short flash excitation in Rhodopseudomonas sphaeroides chromatophores. 24 Apr 44

Glutamate, the major excitatory neurotransmitter in the mammalian central nervous system, is transported into bovine synaptic vesicles in a manner that is ATP dependent and requires a vesicular electrochemical proton gradient. We studied the electrical and chemical elements of this driving force and evaluated the effects of chloride on transport. Increasing concentrations of Cl- were found to increase the steady-state ATP-dependent vesicular pH gradient (delta pH) and were found to concomitantly decrease the vesicular membrane potential (delta psi). Low millimolar chloride concentrations, which cause 3-6-fold stimulation of vesicular glutamate uptake, caused small but measurable increases in delta pH and decreases in delta psi, when compared to control vesicles in the absence of chloride. Nigericin in potassium buffers was used to alter the relative proportions of delta pH and delta psi. Compared to controls, at all chloride concentrations tested, nigericin virtually abolished delta pH and increased the vesicle interior positive delta psi. Concomitantly, nigericin increased ATP-dependent glutamate uptake in 0-1 mM chloride but decreased glutamate uptake in 4 mM (45%), 20 mM (80%), and 140 mM (75%) Cl- (where delta pH in the absence of nigericin was large). These findings suggest that either delta psi, delta pH, or a combination can drive glutamate uptake, but to different degrees. In the presence of 4 mM Cl-, where uptake is optimal, both delta psi and delta pH contribute to the driving force for uptake. When the extravesicular pH was increased from 7.4 to 8.0, more Cl- was required to stimulate vesicular glutamate uptake. In the absence of Cl-, as extravesicular pH was lowered to 6.8, uptake was over 3-fold greater than it was at pH 7.4. As extravesicular pH was reduced from 8.0 toward 6.8, less Cl- was required for maximal stimulation. Decreasing the extravesicular pH from 8.0 to 6.8 in the absence of Cl- significantly increased glutamate uptake activity, even though proton-pumping ATPase activity actually decreased about 45% under identical conditions. In the absence of chloride, nigericin increased glutamate uptake at all the pH values tested except pH 8.0. Glutamate uptake at pH 6.8 in the presence of nigericin was over 6-fold greater than uptake at pH 7.4 in the absence of nigericin. We conclude from these experiments that optimal ATP-dependent glutamate uptake requires a large delta psi and a small delta pH.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Glutamate transport into synaptic vesicles. Roles of membrane potential, pH gradient, and intravesicular pH. 135 94

Digitonin-permeabilized guinea pig spermatozoa undergo acrosomal matrix dispersion in response to 2.0 mM CaCl2. In this report, the effects of pH and metal ions on matrix dispersion in permeabilized spermatozoa are examined. Calcium-induced dispersion of the acrosomal matrix was dependent on the calcium concentration; the response was not observed at concentrations of CaCl2 less than 50 microM. Magnesium could not substitute for calcium and, in fact, had a retarding effect on the calcium-induced response. Matrix dispersion was also found to be pH-dependent. The induction of matrix dispersion was inhibited at pH 5.6 and pH 9.5 relative to the responses observed at pH 6.3 and pH 7.8. Nigericin induced acrosomal matrix dispersion in the absence of added calcium, indicating a possible role of Na+/H+ exchange across the outer acrosomal membrane in initiating the matrix modification. Sodium was required for the action of nigericin; the ionophore was ineffective in medium in which choline chloride or sucrose was substituted for NaCl. In contrast, the calcium-induced dispersion of the acrosomal matrix occurred in the absence of sodium. Furthermore, low concentrations of calcium inhibited an adenosine triphosphatase activity associated with isolated acrosomal apical segments. These data are consistent with the hypothesis that calcium induces alkalinization of the acrosome, leading to matrix dispersion. However, permeabilized spermatozoa incubated at either pH 9.5 or in the presence of 50 mM NH4Cl at pH 7.5 failed to undergo spontaneous matrix dispersion, suggesting that elevated intraacrosomal pH alone was not sufficient to initiate the reaction. The proposed alternative hypothesis is that calcium initiates matrix dispersion by a mechanism in which elevated intraacrosomal pH may be a secondary response.
...
PMID:Regulation of acrosomal matrix dispersion in digitonin-permeabilized guinea pig spermatozoa. 214 57

The apical membrane of the rabbit corneal endothelium contains a potassium-selective ionic channel. In patch-clamp recordings, the probability of finding the channel in the open state (Po) depends on the presence of either HCO3- or Cl- in the bathing medium. In a methane sulfonate-containing bath, Po is less than 0.05 at all physiologically relevant transmembrane voltages. With 0 mM [HCO3-]o at +60 mV, Po was 0.085 and increased to 0.40 when [HCO3-]o was 15 mM. With 4 mM [Cl-]o at +60 mV, Po was 0.083 and with 150 mM Cl-, Po increased to 0.36. Low Po's are also found when propionate, sulphate, bromide, and nitrate are the primary bath anions. The mechanism of action of the anion-stimulated K+ channel gating is not yet known, but a direct action of pH seems unlikely. The alkalinization of cytoplasm associated with the addition of 10 mM (NH4)2SO4 to the bath and the acidification accompanying its removal do not result in channel activation nor does the use of Nigericin to equilibrate intracellular pH with that of the bath over the pH range of 6.8 to 7.8. Channel gating also is not affected by bathing the internal surface of the patch with cAMP, cGMP, GTP-gamma-s, Mg2+ or ATP. Blockers of Na/H+ exchange, Na(+)-HCO3- cotransport, Na(+)-K+ ATPase and carbonic anhydrase do not block the HCO3- stimulation of Po. Several of the properties of the channel could explain some of the previously reported voltage changes that occur in corneal endothelial cells stimulated by extracellular anions.
...
PMID:Potassium channel in rabbit corneal endothelium activated by external anions. 231 91

Calcium (Ca2+) is sequestered into vacuoles of oat root cells through a H+/Ca2+ antiport system that is driven by the proton-motive force of the tonoplast H+-translocating ATPase. The antiport has been characterized directly by imposing a pH gradient in tonoplast-enriched vesicles. The pH gradient was imposed by diluting K+-loaded vesicles into a K+-free medium. Nigericin induced a K+/H+ exchange resulting in a pH gradient of 2 (acid inside). The pH gradient was capable of driving 45Ca2+ accumulation. Ca2+ uptake was tightly coupled to H+ loss as increasing Ca2+ levels progressively dissipated the steady state pH gradient. Ca2+ uptake displayed saturation kinetics with a Km(app) for Ca2+ of 10 microM. The relative affinity of the antiporter for transport of divalent cations was Ca2+ greater than Sr2+ greater than Ba2+ greater than Mg2+. La3+ or Mn2+ blocked Ca2+ uptake possibly by occupying the Ca2+-binding site. Ruthenium red (I50 = 40 microM) and N,N'-dicyclohexylcarbodiimide (I50 = 3 microM) specifically inhibited the H+/Ca2+ antiporter. When driven by pH jumps, the H+/Ca2+ exchange generated a membrane potential, interior positive, as shown by [14C]SCN accumulation. Furthermore, Ca2+ uptake was stimulated by an imposed negative membrane potential. The results support a simple model of one Ca2+ taken up per H+ lost. The exchange transport can be reversed, as a Ca2+ gradient (Ca2+in greater than Ca2+out) was effective in forming a pH gradient (acid inside). We suggest that the H+/Ca2+ exchange normally transports Ca2+ into the vacuole; however, under certain conditions, Ca2+ may be released into the cytoplasm via this antiporter.
...
PMID:Calcium transport into the vacuole of oat roots. Characterization of H+/Ca2+ exchange activity. 242 17

Previous investigation showed two distinct ATP-dependent proton-transporting systems in microsomal vesicle from radish seedlings, one inhibited by vanadate and one inhibited by NO-3. On the bases of the effects of these inhibitors we could discriminate two distinct ATPase activities in the same material. The NO-3 sensitive activity was separated from the vanadate-sensitive activity and partially purified by a single-step chromatographic method, which lead to approx 35-fold purification from the microsomes and to a specific activity of 2.3 mumol Pi X min-1 X mg protein-1, at 30 degrees C. The partially purified activity was specific for ATP, some activity being observed toward GTP, and even less toward CTP, UTP and ITP. No significant Pi hydrolysis was found with ADP, AMP, p-nitrophenylphosphate and glucose 6-phosphate. ADP but not AMP was inhibiting in the presence of ATP. The activity was dependent on divalent cations in the order of preference: Mg2+ greater than Mn2+ greater than Co2+ greater than Ca2+ greater than Zn2+. The activity was unaffected by monovalent cations, strongly activated by Cl-, inhibited by 90% by 50 mM NO-3, virtually unaffected by oligomycin and NaN3. At least 90% of the activity was abolished in the presence of each: 10 microM N,N'-dicyclohexylcarbodiimide, 10 microM erythrosin B, 10 mu mersalyl, 100 microM trimethyltin, 100 microM diethylstilbestrol, 100 microM N-ethylmaleimide. No inhibition has been found in the presence of Ca2+, at a concentration blocking the vanadate-sensitive activity. Nigericin, gramicidin and carbonylcyanide p-trifluoromethoxyphenylhydrazone stimulated the activity of this preparation after it was incubated in the presence of sonicated phospholipids, suggesting the capacity of the ATPase to function as a H+-transporting system. All characteristics mentioned were closely similar to those described in the vacuolar ATPases.
...
PMID:Partial purification and characterization of an anion-activated ATPase from radish microsomes. 285 45

Activation of the Ca2+/Mg2+ ATPase associated with highly purified Torpedo synaptic vesicles results in 45Ca2+ uptake. The accumulated 45Ca2+ is released by hypoosmotic buffer and by the Ca2+ ionophore A23187. Density-gradient centrifugation and permeation chromatography reveal that vesicular acetylcholine and the membrane-bound 45Ca2+ co-migrate, thus implying that 45Ca2+ is transported into cholinergic vesicles. ATP-dependent 45Ca2+ uptake follows saturation kinetics, with KmCa2+ = 50 microM, and Vmax = 3 +/- 0.3 nmol Ca2+/mg protein/min. Treatment of the vesicles with mersalyl, dicyclohexylcarbodiimide, and quercetin leads to inactivation of the Ca2+/Mg2+ ATPase and to comparable inhibition of 45Ca2+ transport. Ruthenium red and ouabain have no effect on either of these activities. Nigericin in the presence of external K+ is a potent inhibitor of 45Ca2+ translocation, whereas gramicidin activates transport. The proton translocator carbonylcyanide p-trifluoromethoxy-phenylhydrazone (FCCP) and FCCP + the ionophore valinomycin partially inhibit 45Ca2+ transport. By contrast, the above ionophores do not affect Ca2+/Mg2+ ATPase activity. Tentative mechanisms for ATP-dependent Ca2+ transport into cholinergic synaptic vesicles and the physiological significance of this process are discussed.
...
PMID:ATP-stimulated Ca2+ transport into cholinergic Torpedo synaptic vesicles. 610 87


1 2 3 Next >>

---