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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Net synthesis of adenosine 5'-triphosphate (ATP) in energy-depleted cells of Escherichia coli was observed when an inwardly directed protonmotive force was artificially imposed. In wild-type cells, ATP synthesis occurred whether the protonmotive force was dominated by the membrane potential (negative inside) or the pH gradient (alkaline inside). Formation of ATP did not occur unless the protonmotive force exceeded a value of 200 mV. Under these conditions, no ATP synthesis was found when cells were exposed to an inhibitor of the membrane-bound Ca2+- and Mg2+- stimulated adenosine triphosphatase (EC 3.6.1.3), dicyclohexylcarbodiimide, or to a proton conductor, carbonylcyanide-p-trifluoromethoxyphenyl-hydrazone. Adenosine triphosphatase-negative mutants failed to show ATP synthesis in response to either a membrane potential or a pH gradient. ATP synthesis driven by a protonmotive force was observed in a cytochrome-deficient mutant. These observations are consistent with the chemiosmotic hypothesis of Mitchell (1961, 1966, 1974).
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PMID:Protonmotive force as the source of energy for adenosine 5'-triphosphate synthesis in Escherichia coli. 0 27

HeLa cell plasma membranes have been purified after binding cells to polylysine-coated polyacrylamide beads. Cell attachment to beads and membrane recovery were maximal in a sucrose-acetate buffer, pH 5.0, at 25 degrees C. Measurements of ouabain-sensitive NaK-adenosine triphosphatase, membrane-bound 125I-wheat germ agglutinin, and chemical analyses showed that membranes on beads were of comparable or greater purity than membranes isolated by conventional methods. Because the isolation procedure is rapid (approximately 2.5 h), and produces membranes whose protoplasmic surfaces are fully exposed, it should be a useful supplement to standard isolation techniques.
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PMID:Membrane isolation on polylysine-coated beads. Plasma membrane from HeLa cells. 2 Nov 92

The effect of inhibitors and uncouplers on the osmotic shock-sensitive transport systems for glutamine and galactose (by the beta-methyl galactoside permease) was compared to their effect on the osmotic shock-resistant proline and galactose permease systems in cytochrome-deficient cells of Salmonella typhimurium SASY28. Both osmotic shock-sensitive and -resistant systems were sensitive to uncouplers and to inhibitors of the membrane-bound Ca2+, Mg2+-activated adenosine triphosphatase. This suggests that uptake by both types of systems is energized in these cells by an electrochemical gradient of protons formed by ATP hydrolysis through the ATPase.
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PMID:Energetics of galactose, proline, and glutamine transport in a cytochrome-deficient mutant of Salmonella typhimurium. 2 79

We have compared the adenosine triphosphatase (ATPase) activity of mitochondria prepared from wild-type Neurospora crassa and from poky, a maternally inherited mutant known to possess defective mitochondrial ribosomes and reduced amounts of cytochromes aa3 and b. poky contains two distinct forms of mitochondrial ATPase. The first is normal in its Km for ATP, specificity for nucleotides and divalent cations, pH optimum, cold stability, and sensitivity to inhibitors (oligomycin, N,N-dicyclohexyl carbodiimide, and adenylyl imidodiphosphate). The fact that membrane-bound, cold-stable, oligomycin-sensitive ATPase activity is present in poky (with an activity of 1.93 +/- 0.03 mumol/min-mg of protein compared with 1.33 +/- 0.07 mumol/min-mg of protein in the wild-type strain) and also in chloramphenicol-grown wild-type cells suggests that products of mitochondrial protein synthesis play only a limited role in the attachment of the mitochondrial ATPase to the membrane in Neurospora. poky also contains a second form of mitochondrial ATPase, which has an activity of 1.5 +/- 0.2 mumol/min-mg of protein, is oligomycin sensitive but cold labile, and presumably is attached less firmly to the mitochondrial membrane. The two forms, added together, represent a substantial overproduction of mitochondrial ATPase by poky.
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PMID:Mitochondrial adenosine triphosphatase of wild-type and poky Neurospora crassa. 2 38

The membrane-bound adenosine triphosphatase (ATPase) activity of Acholeplasma laidlawii B differs in many respects from the common (Mg2+, Ca2+)-ATPase activity of higher bacteria, most notably in that it is specifically activated by Mg2+ and strongly and specifically stimulated by Na+ (or Li+). Various inhibitors diminish the ATPase activity with a concentration dependence which suggests that a single enzyme species is responsible for all of the observed ATP hydrolytic activity (both basal and Na+ stimulated). The Km for ATP is influenced by temperature but not by membrane lipid fatty acid composition. Vmax is influenced by both of these factors, showing a break in Arrhenius plots which falls below the lipid phase transition midpoint but well above the lower boundary when a phase transition occurs within the temperature range studied. The apparent energy of activation for Vmax is strongly influenced by lipid fatty acid composition both above and below the break. When whole cells of A. laidlawii B are incubated in KCl or NaCl buffers, they rapidly swell and lyse if deprived of an energy source or treated with ATPase inhibitors at concentrations which significantly inhibit enzyme activity in isolated membranes, whereas in sucrose or MgSO4 buffers of equal osmolarity, the cells are stable under these conditions. These results suggest that the membrane ATPase of A. laidlawii B is intimately associated with the membrane lipids and that it functions as a monovalent cation pump which regulates intracellular osmolarity as the (Na+, K+)-ATPase does in eucaryotes.
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PMID:Physiological role and membrane lipid modulation of the membrane-bound (Mg2+, na+)-adenosine triphosphatase activity in Acholeplasma laidlawii. 3 51

Lactobacillus casei cells can accumulate folate to an intracellular concentration in excess of 500 muM and to concentration gradients (relative to the extracellular compartment) of several thousand-fold. Maximum rates of folate transport are achieved rapidly (t(1/2) < 1 min) after the addition of glucose to energy-depleted cells and occur at intracellular adenosine 5'-triphosphate concentrations above 625 muM. The rate of folate transport and the adenosine 5'-triphosphate content of cells are both extremely sensitive to arsenate and decrease in parallel with increasing concentrations of the inhibitor, indicating a requirement for phosphate-bond energy in the transport process. The energy source is not a membrane potential or a pH gradient generated via the membrane-bound adenosine triphosphatase, since dicyclohexylcarbodiimide (an adenosine triphosphatase inhibitor) and carbonyl cyanide m-chlorophenylhydrazone (a proton conductor) have little effect on the uptake process. The K(+)-ionophore, valinomycin, is an inhibitor of folate transport, but does not act via a mechanism involving dissipation of the membrane potential. This can be deduced from the facts that the inhibition by valinomycin is relatively insensitive to pH, is considerably greater in Na(+)- than in K(+)-containing buffers, and is not enhanced by the addition of proton conductors. Folate efflux is not affected by valinomycin, glucose, or various metabolic inhibitors, although a rapid release of the accumulated vitamin can be achieved by the addition of unlabeled folate together with an energy source (glucose). These results suggest that the active transport of folate into L. casei is energized by adenosine 5'-triphosphate or an equivalent energy-rich compound, and that coupling occurs not via the membrane-bound adenosine triphosphatase but by direct interaction of the energy source with a component of the transport system.
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PMID:Coupling of energy to folate transport in Lactobacillus casei. 11 Jul 91

Cytochalasin A at 10-20 mug/ml inhibits growth and sugar uptake by Saccharomyces strain 1016. The effects of cytochalasin A in intact cells were completely prevented when 1 mM cysteine or dithiothreitol was added along with cytochalasin A, but were not eliminated by thiols added after inhibition had occurred. Purified yeast hexokinase, glucose-6-P dehydrogenase, phosphofructokinase and aldolase were not sensitive to cytochalasin A (20 mug/ml). Glyceraldehyde-3-P dehydrogenase was strongly inhibited by cytochalasin A (5 mug/ml); activity was promptly restored by thiols. Anaerobic glycolysis was inhibited by cytochalasin A or by iodoacetate; unlike iodoacetate, cytochalasin A did not cause accumulation of sugar phosphates. In contrast, cytochalasin A, but not iodoacetate, inhibited isolated membrane-bound ATPases. Cytochalasin A is a sulfhydryl-reactive agent and has membrane-related effects (adenosine triphosphatase) which may well be the basis of its interference with energy-dependent uptake of solutes.
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PMID:Action of cytochalasin A, a sulfhydryl-reactive agent, on sugar metabolism and membrane-bound adenosine triphosphatase of yeast. 12 88

An abnormal flux of monovalent cations may be related to the epileptogenic process in man. One possible mechanism for deranged electrolyte metabolism in epileptic brain is an abnormality in sodium, potassium-dependent adenosine triphosphatase (Na, K ATPase). We found the activity of Na, K ATPase to be significantly less in epileptic human corfex than in nonepileptic cortex. Histological changes have been simultaneously evaluated in epileptic brain. A second membrane-bound enzyme, acetylcholinesterase (AChE), was also assayed as a marker for neuronal membranes and found not to correlate with the epileptogenicity of human brain. In addition, the concentrations of the anticonvulsant compound phenytoin have been determined in the serum and cerebral cortex of epileptic and nonepileptic patients. The ratio of phenytoin in cortex to serum concentration is significantly lower in epileptic patients than in nonepileptic controls.
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PMID:Human epileptic brain Na, K ATPase activity and phenytoin concentrations. 12 76

The lipid composition of yeast cells was manipulated by the use of an unsaturated fatty acid auxotroph of Saccharomyces cerevisiae. There was a 2-3-fold decrease in the concentration of cytochromes a+a3 when the unsaturated fatty acid content of the cells was decreased from 60-70% of the total fatty acid to 20-30%. The amounts of cytochromes b and c were also decreased under these conditions, but to a lesser extent. Further lipid depletion, to proportions of less than 20% unsaturated fatty acid, led to a dramatic decrease in the content of all cytochromes, particularly cytochromes a+a3. The ATPase (adenosine triphosphatase), succinate oxidase and NADH oxidase activities of the isolated mitochondria also varied with the degree of unsaturation of the membrane lipids. The lower the percentage of unsaturated fatty acid, the lower was the enzymic activity. Inhibition of mitochondrial ATPase by oligomycin, on the other hand, was not markedly influenced by the membrane-lipid unsaturation. Npn-linear Arrenius plots of mitochondrial membrane-bound enzymes showed transition temperatures that were dependent on the degree of membrane-lipid unsaturation. The greater the degree of lipid unsaturation, the lower was the transition temperature. It was concluded that the degree of unsaturation of the membrane lipids plays an important role in determining the properties of mitochondrial membrane-bound enzymes.
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PMID:Membrane-lipid unsaturation and mitochondrial function in Saacharomyces cerevisiae. 12 85

1. The uptakes of Pi and serine by whole cells of mutant strains of Escherichia coli K12, grown under both aerobic and anaerobic conditions, were studied. 2. Uptake by aerobic cells was low in a ubiquinone-less mutant but normal in two mutant strains unable to couple phosphorylation to electron transport. 3. One of these uncoupled strains, carrying the unc-405 allele, does not form a membrane-bound Mg2+-stimulated adenosine triphosphatase aggregate, and it is concluded that the Mg2+-stimulated adenosine triphosphatase does not serve a structural role in the aerobic active transport of Pi or serine. 4. The other uncoupled strain, in which aerobic uptake is unaffected, carries a mutation in the uncB gene, thus distinguishing this gene from the etc gene, previously shown to be concerned with the coupling of electron transport to active transport. 5. The uptakes of Pi and serine by anaerobic cells were normal in the ubiquinone-less mutant, but defective in both the uncoupled strains. 6. The uptake of Pi and serine by anaerobic cells of the uncB mutant could be increased by the addition of fumarate to the uptake medium. The unc-405 mutant, however, required the addition of fumarate for growth and for uptake. 7. The uncB mutant, unlike the unc-405 mutant, is able to grow anaerobically in a minimal medium with glucose as sole source of carbon. Similarly a strain carrying a mutation in the frd gene, which is the structural gene for the enzyme fumarate reductase, is able to grow anaerobically in a glucose-minimal medium. However, a mutant strain carrying mutations in both the uncB and frd genes resembles the unc-405 mutant in not being able to grow under these conditions.
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PMID:Metabolite transport in mutants of Escherichia coli K12 defective in electron transport and coupled phosphorylation. 12 86


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