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At least 595 records · Page 33Linked to original sources
PubMed1996

Thyroid status and adenosine triphosphatase activity in experimental Trypanosoma congolense infection in rabbits.

The effect of trypanosome infection on the plasma levels and ratios of tri-iodothyronine (T3) and thyroxine (T4) as well as the activity of mitochondrial adenosine triphosphatase (ATPase) were investigated. Three groups of sexually mature white New Zealand rabbits were used. Group 1 consisted of the normal non-infected rabbits, group 2 were experimentally infected with Trypanosoma congolense and group 3 were infected but given replacement doses of thyroxine. The infected animals (group 2) showed a rapid decline in both T3 and T4 but an increase in the T3/T4 ratio indicating differential production or clearance rates between the two hormones. The mitochondrial ATPase activity was found to be depressed in the infected group whereas there was no significant difference in the ATPase activity between the non-infected (group 1) and infected-treated animals (group 2). It is postulated that trypanosome induced hypothyroid status may play a role in the impairment of mitochondrial ATPase activity, a key enzyme in energy metabolism.

Adenosine Triphosphatases↗
PubMed1981

Effects of quercetin on magnesium-dependent adenosine triphosphatase and the metabolism of human polymorphonuclear leukocytes.

The bioflavinoid quercetin was found to exert at least three separate effects on human polymorphonuclear leukocytes. (1) Concentrations of approximately 100 microM inhibited the membrane-associated magnesium adenosine triphosphatase by 60%-80% in either broken cell preparations or intact cells. Lineweaver-Burk plots showed the inhibition to be uncompetitive in nature. (2) Similar concentrations of quercetin inhibited respiratory burst activity of the cells as measured by oxygen consumption, glucose oxidation, or iodination of protein. All inhibitions were dose-dependent and were observed with either opsonized zymosan or phorbol myristate acetate as stimulus. (3) Quercetin likewise inhibited the transport of the nonmetabolizable hexose, 3H-2-deoxyglucose. These observations are most consistent with the hypothesis that quercetin exerts a generalized effect at the level of the cell membrane of the neutrophil.

Adenosine Triphosphatases↗
PubMed1986

Adenosine triphosphatase activity of crystalline inclusions in alveolar soft part sarcoma. An ultrahistochemical study of a case.

A case of alveolar soft part sarcoma was studied by light and electron microscopy and by electron microscopic enzyme histochemistry of adenosine triphosphatase (ATPase) and 5'nucleotidase(5'Nase). The tumor showed distinct alveolar pattern and diastase resistant PAS positive crystalline inclusions were found in the cytoplasm. Ultrastructurally, characteristic rhomboid crystals and dense granules were observed and they were positive for Mg++- and Ca++-ATPases but negative for 5'Nase. Tumor cell membrane also showed positive activity of ATPase in addition to 5'Nase. These results would support the myogenous derivation of alveolar soft part sarcoma.

5'-Nucleotidase↗
PubMed1981

Divalent metals in beef heart mitochondrial adenosine triphosphatase. Demonstration of the metals in membrane-bound enzyme and studies of the interconversion of the "1-Mg" and "2-Mg" forms of the enzyme.

Tight divalent metal binding sites in the beef heart mitochondrial adenosine triphosphatase were studied using the procedure of reconstitution of soluble F1 with F1-depleted membranes (SU particles). Soluble F1 has been shown previously to contain two tight-binding site for Mg. Both of these sites were present on membrane-bound enzyme. Co and Mn, substituted at the second of the two Mg-binding sites on soluble F1, became incorporated with F1 into membrane-bound enzyme. Use of radioactive Co and Mn showed that they behaved differently during short bursts of succinate oxidation or ATP hydrolysis. Co remained stably bound, whereas Mn was released to the extent of 55-80%. The results extend previous work to show that the membrane proton-ATPase is an Mg-metalloenzyme containing a structural Mg site and a second Mg site possibly involved in catalysis. The conversion of 2-Mg F1 to 1-Mg F1 during purification and storage is shown to be due to use of ammonium sulfate precipitation, and the dependence of reuptake of Mg (1-Mg F1 leads to 2-Mg F1) on nucleotides is described.

Adenosine Triphosphatases↗
PubMed1977

Mitochondrial adenosine triphosphatase of the fission yeast Schizosaccharomyces pombe 972h-. Changes in inhibitor sensitivities during the cell cycle indicate similarities and differences in binding sites.

1. We used 11 different inhibitors of energy conservation as inhibitors of ATPase (adenosine triphosphatase) in extracts of Schizosaccharomyces pombe obtained from cells at different stages of the cell cycle. 2. All the inhibitors showed cell-cycle-dependent variations in their I50 values (microng of inhibitor/mg of protein giving 50% inhibition of inhibitor-sensitive ATPase at pH 8.6). 3. From the sensitivity profiles through the cell cycle it was concluded that: (a) oligomycin, venturicidin, triethyltin sulphate and dibutylchloromethyltin chloride all act at closely associated site(s); (b) NN'-dicyclohexylcarbodi-imide and leucinostatin both act at a similar site, which is, however, distinct from that at which other inhibitors of the membrane factor (Fo) act. 4. The variations in I50 values for efrapeptin closely followed changes in specific activity of ATPase, as would be expected for an inhibitor acting at catalytic sites; these fluctuations were different from those for aurovertin, Dio-9, 4-chloro-7-nitrobenzofurazan, quercetin and spegazzinine, all of which show different sensitivity profiles from one another. 5. Anomalous stepwise inhibitor-titration curves were obtained for spegazzinine, NN'-dicyclohexylcarbodiimide, dibutylchloromethyltin chloride and leucinostatin. 6. Possible explanations are proposed for the discontinuous expression of inhibitor-binding sites during the cell cycle.

Adenosine Triphosphatases↗
PubMed1988

Localisation of calcium-activated adenosine-triphosphatase (Ca2+-ATPase) in intracerebral arterioles in acute hypertension.

The plasma membrane calcium-activated adenosine triphosphatase (Ca2+-ATPase) is known to regulate intracellular calcium levels. This enzyme was localised in intracerebral cortical vessels of normotensive and acutely hypertensive rats. Of interest was whether the arterioles that develop increased permeability to horseradish peroxidase (HRP) in acute hypertension demonstrate any alteration in localisation of Ca2+-ATPase as compared to normotensive controls. Rats were injected with HRP intravenously and acute hypertension was induced by a 2-min infusion of angiotensin amide. Following perfusion of fixative, brains were sliced and reacted for demonstration of HRP reaction product and Ca2+-ATPase. Normotensive rats showed discontinuous distribution of Ca2+-ATPase on the outer plasma membranes of endothelial, smooth muscle and adventitial cells of arterioles. The localisation of Ca2+-ATPase in pinocytotic vesicles present in endothelial and smooth muscle cells was quite striking. Focal cortical areas of hypertensive rats showed increased arteriolar permeability to HRP. Permeable arterioles showed marked reduction of Ca2+-ATPase on the outer plasma membranes of endothelium and smooth muscle cells as compared to nonpermeable arterioles of the same animals and arterioles of normotensive controls. The latter finding suggests that calcium may be involved in increased cerebrovascular permeability mechanisms in acute hypertension.

Animals↗
PubMed1986

Insulin stimulates renal glomerular sodium-potassium adenosine triphosphatase activity.

The effect of insulin on total and ouabain-inhibited membrane-bound adenosine triphosphatase (ATPase) activity in renal glomeruli isolated from adult white rats was examined. In concentrations of 1-10 micrograms/ml, insulin significantly stimulated the ouabain-inhibited (Na+ + K+)-ATPase activity, without affecting total (composite) ATPase activity. These results, coupled with previous findings demonstrating that glomerular (Na+ + K+)-ATPase activity is reduced in acute streptozotocin diabetes, suggest that the renal glomerulus is a target tissue with respect to this biologic effect of insulin.

Animals↗
PubMed1990

Sodium/potassium adenosine triphosphatase alpha-subunit and alpha-subunit mRNA levels in early rabbit embryos.

Sodium/potassium adenosine triphosphatase (Na+/K+ ATPase) and Na+/K+ ATPase mRNA content of rabbit embryos during preimplantation development were evaluated. Changes in Na+/K+ ATPase alpha-subunit content were detected with Western blotting using polyclonal antiserum against guinea pig Na+/K+ ATPase. Total RNA samples from rabbit embryos were analyzed by using Northern blots hybridized with random primer-labeled cDNA for Na+/K+ ATPase alpha-subunit from sheep kidney. Northern blots exhibited a single mRNA band (3.65 kilobases) in sheep kidneys and rabbit embryos. Between Day 4 and Day 6 of development, Na+/K+ ATPase alpha-subunit mRNA content increased 35-fold whereas Na+/K+ ATPase alpha-subunit content increased 22-fold. The similar increase in Na+/K+ ATPase alpha-subunit mRNA and alpha-subunit content in rabbit embryos suggests that Na+/K+ ATPase is partly regulated at the mRNA level during blastocyst expansion.

Animals↗
PubMed1979

Partial Characterization of a Potassium-stimulated Adenosine Triphosphatase from the Plasma Membrane of Meristematic and Mature Soybean Root Tissue.

A K(+)-stimulated adenosine triphosphatase was partially characterized in plasma membrane from meristematic and mature soybean root tissue. The substrate concentrations required for maximum enzyme activity (3 millimolar Mg.ATP) and pH optimum (6.5) were similar for both systems. Enrichment studies, performed to ensure that the membrane vesicle preparations were comparable, indicated similar purity levels at selected steps during purification. Phospholipid and sterol analyses further substantiated their similarity.Enzyme studies revealed significantly greater ATPase activity, per unit membrane protein, in the meristematic region. Mixing experiments indicated that the lower level of activity associated with vesicles from mature tissue was not due to endogenous inhibitor(s).

Journal Article↗
PubMed2000

Luminal localization of blood-brain barrier sodium, potassium adenosine triphosphatase is dependent on fixation.

Cytochemical data in the literature reporting localization of sodium, potassium adenosine triphosphatase (Na(+), K(+)-ATPase) in the blood-brain barrier (BBB) have been contradictory. Whereas some studies showed the enzyme to be located exclusively on the abluminal endothelial plasma membrane, others demonstrated it on both the luminal and abluminal membranes. The influence of fixation on localization of the enzyme was not considered a critical factor, but our preliminary studies showed data to the contrary. We therefore quantitatively investigated the effect of commonly used fixatives on the localization pattern of the enzyme in adult rat cerebral microvessels. Fixation with 1%, 2%, and 4% formaldehyde allowed deposition of reaction product on both the luminal and abluminal plasma membranes. The luminal reaction was reduced with increasing concentration of formaldehyde. Glutaraldehyde at 0.1%, 0.25%, 0.5%, in combination with 2% formaldehyde, drastically inhibited the luminal reaction. The abluminal reaction was not significantly altered in all groups. These results show that luminal localization of BBB Na(+), K(+)-ATPase is strongly dependent on fixation. The lack of luminal localization, as reported in the literature, may have been the result of fixation. The currently accepted abluminal polarity of the enzyme should be viewed with caution.

Animals↗
PubMed1985

Structure-activity relationship of bufotoxins and related compounds for the inhibition of Na+, K+ -adenosine triphosphatase.

Forty kinds of bufotoxins and related compounds were tested for inhibition of Na+, K+ -adenosine triphosphatase from guinea pig heart, and the structure-activity relationship has been discussed. The inhibitory activities of bufotoxins were dependent upon the dicarboxylic acid and amino acid components. The compounds having both the arginine and suberic acid moieties showed the higher inhibitory activities. The sulfates and glucuronides of cardiac steroids exhibited much less potency than the parent genins. The mode of inhibition was determined by means of the Dixon and Lineweaver-Burk plots.

Animals↗
PubMed1990

Molecular structure of a gene, VMA1, encoding the catalytic subunit of H(+)-translocating adenosine triphosphatase from vacuolar membranes of Saccharomyces cerevisiae.

Subunit a of the vacuolar membrane H(+)-translocating adenosine triphosphatase of the yeast Saccharomyces cerevisiae contains a catalytic site for ATP hydrolysis. N-terminal sequences of six tryptic peptides of the subunit were determined. Based on the peptide sequence information, a 39-base oligonucleotide probe was synthesized, and the gene encoding the subunit (VMA1) was isolated from a genomic DNA library by hybridization. The nucleotide sequence of the gene predicts a polypeptide of 1,071 amino acids with a calculated molecular mass of 118,635 daltons, which is much larger than the value 67 kDa estimated on sodium dodecyl sulfate-polyacrylamide gels. N- and C-terminal regions of the deduced sequence (residues 1-284 and 739-1,071) are very similar to those of the catalytic subunits of carrot (69 kDa) and Neurospora crassa (67 kDa) vacuolar membrane H(+)-ATPases (62 and 73% identity over 600 residues, respectively). The homologous regions also show about 25% sequence identity over 400 residues with beta-subunits of F0F1-ATPases. In contrast, the internal region containing 454 amino acid residues (residues 285-738) shows no detectable sequence similarities to any known ATPase subunits and instead is similar to a yeast endonuclease encoded by the HO gene. None of the six tryptic peptides is located in this internal region. Northern blotting analysis detected a single mRNA of 3.5 kilobases, indicating that the gene has no introns. Although the reason for the discrepancy in molecular mass is unclear at present, these results suggest that a novel processing mechanism, which might involve a post-translational excision of the internal region followed by peptide ligation, operates on the yeast VMA1 product. The VMA1 gene has proven to be the same gene as the TFP1 gene (Shih, C.-K., Wagner, R., Feinstein, S., Kanik-Ennulat, C., and Neff, N. (1988) Mol. Cell. Biol. 8, 3094-3103) whose dominant mutant allele (TFP1-408) confers a dominant trifluoperazine resistance and Ca2(+)-sensitive growth. This and our findings suggest that the vacuolar membrane H(+)-ATPase participates in maintenance of cytoplasmic Ca2+ homeostasis.

Amino Acid Sequence↗
PubMed1981

The NH2 terminus of the (Ca2+ + Mg2+)-adenosine triphosphatase is located on the cytoplasmic surface of the sarcoplasmic reticulum membrane.

The (Ca2+ + Mg2+)-adenosine triphosphatase (ATPase) of sarcoplasmic reticulum contains a cysteine residue at position 12 of its sequence. This sulfhydryl group was 1 out of a total of 10-11 that were labeled by treatment of sarcoplasmic reticulum vesicles with N-[3H]ethylmaleimide under saturating conditions. This was shown by isolating a 31-residue NH2-terminal peptide from a tryptic digest of the succinylated ATPase, prepared from N-[3H]ethylmaleimide-labeled vesicles. Reaction of the vesicles with glutathione maleimide, parachloromercuribenzoic acid, or parachloromercuriphenyl sulfonic acid, membrane-impermeant reagents, prevented further reaction of sulfhydryl groups with N-ethylmaleimide. This result indicates that all sulfhydryl groups that are reactive with N-ethylmaleimide are on the outside of the vesicles. Since Cys12 is located in a hydrophilic NH2-terminal portion of the ATPase, the labeling results suggest that the NH2 terminus of the ATPase is on the cytoplasmic side of the membrane. These results are consistent with earlier observations (Reithmeier, R. A. F., de Leon, S., and MacLennan, D. H. (1980) J. Biol. Chem. 255, 11839-11846) that the (Ca2+ + Mg2+)-ATPase is synthesized without an NH2-terminal signal sequence.

Amino Acid Sequence↗
PubMed1976

A reassessment of the phospholipid dependence of membrane-bound enzymes, with special reference to glucose-6-phosphatase and Na+, K+-dependent adenosine triphosphatase.

It is suggested that the specific involvement of phospholipid in either the expression or constraint of glucose-6-phosphatase activity is not conclusively established by the existing experimental evidence. The physiological significance of an apparent requirement for phosphatidylserine for Na+, K+-dependent adenosine triphosphatase activity is also questioned. The need for a critical reassessment of past conclusions in the light of present knowledge is emphasized.

Adenosine Triphosphatases↗
PubMed1979

Properties of membranes from mutant strains of Escherichia coli in which the beta-subunit of the adenosine triphosphatase is abnormal.

Five uncoupled mutant strains of Escherichia coli carrying mutations in the uncD gene have been studied. In each of these mutant strains the beta-subunit of the F1 portion of the membrane-bound adenosine triphosphatase is abnormal. In one of the mutant strains (carrying the uncD12 allele) in F1-ATPase aggregate was formed which was purified and found to have low ATPase activity. ATPase activity was absent in the other four strains and the abnormal beta-subunits were tightly bound to the membranes. However, membranes from these strains exhibited various proton permeabilities as indicated by NADH-dependent atebrin-fluorescence quenching and bound different amounts of normal F1-ATPase. The amounts of reconstitution of energy-linked reactions after the addition of normal F1-ATPase also varied depending on the mutant allele. It is apparent that considerable phenotypic variations can occur between strains carrying mutations in the same unc gene.

Adenosine Triphosphatases↗
PubMed1981

Assembly of the adenosine triphosphatase complex in Escherichia coli: assembly of F0 is dependent on the formation of specific F1 subunits.

A strain of Escherichia coli (AN1007) carrying the polar uncD436 allele which affects the operon coding for the F1-F0 adenosine triphosphatase (ATPase) complex was isolated and characterized. The uncD436 allele affected the two genes most distal to the operon promoter, i.e., uncD and uncC. Although the genes coding for the F0 portion of the ATPase complex were not affected in strains carrying this mutant allele, the lack of reconstitution of washed membranes by normal F1 ATPase suggested that a functional F0 might not be formed. This conclusion was supported by the observation that the 18,000-molecular-weight F0 subunit, coded for by the uncF gene, was absent from the membranes. Plasmid pAN36 (uncD+C+), when inserted into a strain carrying the uncD436 allele, resulted in the incorporation of the 18,000-molecular-weight F0 subunit into the membrane. A further series of experiments with Mu-induced polarity mutants, with and without plasmid pAN36, showed that the formation of both the alpha- and beta-subunits of F1 ATPase was an essential prerequisite to the incorporation into the membrane of the 18,000-molecular-weight F0 subunit and to the formation of a functional F0. Examination of the polypeptide composition of membranes from various unc mutants allowed a sequence for the normal assembly of the F1-F0 ATPase complex to be proposed.

Adenosine Triphosphatases↗