The calcium binding sites involved in the regulation of the purified adenosine triphosphatase of the sarcoplasmic reticulum.
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Adenosine Triphosphatases↗
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Energy-dependent enhancement of aurovertin fluorescence. An indicator of conformational changes in beef heart mitochondrial adenosine triphosphatase.
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Adenosine Diphosphate↗
Solubilization & properties of an adenosine triphosphatase of reo virus.
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Adenosine Triphosphatases↗
Copper-transporting P-type adenosine triphosphatase (ATP7B) is expressed in human breast carcinoma.
This is the first report to show that a copper-transporting P-type adenosine triphosphatase, ATP7B, is expressed in certain breast carcinomas, and a priori knowledge of its expression is important for the choice of therapy. We investigated the hypothesis that ATP7B, which was shown to be associated with cisplatin resistance in vitro, is expressed in certain breast carcinomas. To test this hypothesis, ATP7B expression and protein level were examined in 41 breast carcinomas using RT-PCR and immunohistochemistry. ATP7B gene / protein could be detected in 22.0% (9 / 41) of breast carcinomas and ATP7B gene expression was correlated well with the protein expression. In nine ATP7B-positive tumors, adjacent normal breast tissue was similarly analyzed, revealing that ATP7B is upregulated in breast carcinoma. ATP7B gene expression in poorly differentiated carcinoma was significantly higher than that in well- / moderately differentiated carcinoma (P = 0.012). Furthermore, we found no association between the ATP7B gene / protein expression and that of MDR1, MRP1, LRP and BCRP. These findings suggested that ATP7B gene expression might be a chemoresistance marker for cisplatin in patients with poorly differentiated breast carcinoma.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Mg2+ adenosine triphosphatase from cell envelopes of free-living and bacteroid forms of Rhizobium lupini strain NZP2257.
A procedure for the purification of Mg2+ adenosine triphosphatase (EC 3.6.1.3) from free-living and bacteroid forms of Rhizobium lupini NZP2257 is described. The enzyme was released from cell envelopes using Triton X-100 and purified by gel filtration on Ultrogel AcA 22, followed by preparative gel electrophoresis on agarose. The purified ATPase had a molecular weight of about 355,000, as determined from sedimentation coefficients on sucrose gradients. Kinetic analysis of activity of the enzyme from free-living R. lupini showed it to be typical of F1-type Mg2+ ATPases from bacteria. Mg stimulated activity at pH 7.0, although, when present as the free ion, Mg caused non-competitive inhibition (K1 = 1.5 mM). Maximum activity with ATP occurred over a broad pH range from 6.0 to 10.5. ATP, GTP, and UTP, and, to a much lesser degree, CTP and ADP, were hydrolyzed by the enzyme. Hydrolysis of glucose 6-phosphate was not observed. The Km for ATP at pH 7.0 was 0.67 and for GTP 1.4 mM. ATPase activity was inhibited by ADP, and competitive with ATP (KI = 0.18 mM). Azide also caused inhibition but fluoride and DCCD had no effect. Native and sodium dodecyl sulfate-gel electrophoretic analysis revealed no obvious differences between ATPases from free-living and bacteroid forms of R. lupini.
Adenosine Triphosphatases↗
Vanadate stimulates the N-ethylmaleimide-sensitive adenosine triphosphatase in rat nephron.
Vanadate has been used in many cellular systems to elucidate mechanisms of enzyme action. Vanadate inhibits Na-K adenosine triphosphatase (ATPase) activity in many tissues. In isolated collecting tubule it inhibits sodium transport and vasopressin-stimulated water flux, the latter presumably distal to cyclic AMP formation. Depending upon the tissue studied, vanadate also stimulates a variety of cellular reactions including adenylate cyclase, glucose oxidation and glycogen synthesis. We studied the effect of varying concentrations of vanadate on N-ethylmaleimide (NEM)-sensitive ATPase activity in microdissected segments of rat nephron. In proximal convoluted tubule and in cortical, medullary and papillary collecting ducts vanadate had no effect on enzyme activity. In medullary and cortical thick ascending limbs, however, vanadate significantly stimulated NEM-sensitive ATPase activity (medullary thick ascending limb, 241 +/- 14 pmol/mm/hr vs. 531 +/- 74 pmol/mm/hr; control vs. (1 mM) vanadate, respectively; n = 14, P less than 0.01). The stimulatory effect of vanadate on NEM-sensitive ATPase activity was present at 5 microM vanadate, a concentration that inhibited Na-K ATPase activity approximately 80%. Metabolic acidosis also stimulated enzyme activity in the thick ascending limb, and the effect of vanadate was not additive. Metabolic alkalosis had no effect on NEM-sensitive ATPase in the thick ascending limb, but the stimulatory effect of vanadate was still seen. These data document that the NEM-sensitive ATPase in thick ascending limb is different from that found in other nonmammalian proton secretory epithelia which are vanadate inhibitable. The results with vanadate plus metabolic acidosis suggest that both are acting via the same mechanism.
Acidosis↗
Hepatic and renal phosphomonoesterases and adenosine triphosphatases in chronic hyperprolactinaemic rats.
Influence of hyperprolactinaemia, induced endogenously by anterior pituitary transplantation on rat hepatic and renal cortical and medullary phosphomonoesterases and adenosine triphosphatases (ATPases) has been investigated. Although prolactin has a stimulatory effect on phosphomonoesterases and ATPases, it exhibits a specific and temporal influence on each subtype of hepatic and renal ATPases and phosphomonoesterases at different durations of pituitary transplantation. The specific activities of alkaline phosphatase and Na(+)-K+ dependent ATPases are activated in all the regions of different durations of experimentation. However, acid phosphatases, Ca2+ and Mg2+ dependent ATPases exhibit a differential response to prolactin in renal cortex, medulla and liver. Direct influence of prolactin on hepatic and renal phosphomonoesterases and ATPases is thus suggested.
Adenosine Triphosphatases↗
Characterization and comparison of metal accumulation in two Escherichia coli strains expressing either CopA or MntA, heavy metal-transporting bacterial P-type adenosine triphosphatases.
MntA from Lactobacillus plantarum and copA from Enterococcus hirae both encode membrane proteins that are members of the P-type family of adenosine triphosphatases (ATPases). Both transporters act as metal importers to take up nutritionally required substrates; MntA translocates Mn(II) and CopA translocates Cu(I). Both ATPases can also translocate secondary substrates, Cd(II) and Ag(I), respectively. Although functionally and sequentially similar, these ATPases differ in several key residues and in their membrane topologies. The bioaccumulation properties of these two proteins were examined by coexpressing the transporters with overexpressed metallothionein in Escherichia coli cells, a system that has previously shown high levels of substrate-specific uptake. Both strains exhibited rapid metal accumulation, both saturated at around 50 microM metal, and both displayed temperature-sensitive uptake. However, the transporters responded differently when external conditions were varied; MntA displayed increased sensitivity to ionic strength, while CopA was more pH sensitive and more inhibited by chelating agents. The differences in accumulation are likely owing to structural differences in the transmembrane region of these two ATPases.
Adenosine Triphosphatases↗
Adenosine triphosphatase systems in genital tract of testosterone treated male adult monkeys.
Studies on the distribution of Na+, K+-dependent, Mg2+ dependent and Ca2+ dependent Adenosine Triphosphatase (ATP-ases) in the testes, epididymis, seminal vesicles and prostate glands of mature bonnet monkeys were carried out with and without Testosterone propionate (TP) treatment. Comparatively, the Ca2+ dependent ATP-ase was very active in the testes, caput and cauda epididymis and prostate of control animals. However, the Mg2+-dependent ATP-ase activity was predominant in the seminal vesicles. In all the genital tissues the Na+, K+ dependent ATP-ase exhibited low activity compared to other ATP-ase systems. On TP treatment at 1 mg/kg body wt. dose for 30 consecutive days to the second group of animals, all classes of ATP-ases drastically decreased in the testes, cauda epididymis, seminal vesicles and prostate. While in caput epididymis the Mg2+-dependent ATP-ase was stimulated, the Na+, K+-dependent ATP-ase was decreased both in the caput and corpus epididymis by the hormone treatment. The present study reveals the general inhibitory influence on the ATP-ase systems and thereby ionic transport after long term TP administration.
Adenosine Triphosphatases↗
Cytochemical studies on the localization of alkaline phosphatase and HCO-3-activated adenosine triphosphatase in the brush border membrane of rat duodenal enterocytes.
Cytochemical techniques were used to demonstrate, with appropriate controls, alkaline phosphatase and HCO-3-activated adenosine triphosphatase (ATPase) in rat duodenal brush border microvillus membranes. Intense activity of ecto-alkaline phosphatase activity was demonstrated with 2-glycerophosphate as substrate. Although biochemical assays suggested that L-phenylalanine inhibited both alkaline phosphatase and HCO-3-activated ATPase, cytochemical studies indicated that there was marked inhibition of alkaline phosphatase revealing a specific HCO-3-activated ATPase on the inner aspect of the microvillus membrane. While it is tempting to suggest that this HCO-3-activated ATPase is implicated in active bicarbonate secretion by the duodenum, decisive identification is not yet possible.
Adenosine Triphosphatases↗
Adenosine triphosphatases of rat cerebral microvessels. Effect of age and diabetes mellitus.
To determine the effect of age and diabetes mellitus on the activity of various adenosine triphosphatases (ATPases) of cerebral microvessels, streptozotocin-induced diabetic rats, and aged rats (26 months old) were compared to young control rats (4 months old). The results indicate that diabetic rats have reduced ATPase inhibition by N-ethylmaleimide (NEM), a vacuolar proton (H+)-ATPase inhibitor (98.7 +/- 0.81% vs 78.9 +/- 4.3% of buffer, p < 0.05). Aged rat cerebral microvessels also had reduced NEM sensitive ATPase activity. Sodium-potassium (Na(+)-K(+)-) or magnesium ATPase activity of cerebral microvessels was not altered with diabetes or aging. The changes in cerebral microvessels were distinct from those found in synaptosomal membranes indicating cell specificity of the findings. The results indicate that the age-related and diabetes-related changes in the activity of ATPases in cerebral microvessels are similar but not identical. These changes may contribute to the altered blood-brain barrier functions found in diabetic and aged rats.
Adenosine Triphosphatases↗
Optical properties and denaturation by guanidinium chloride and urea of the adenosine triphosphatase of Micrococcus lysodeikticus. A comparison of four molecular forms of the enzyme.
1. The fluorescence and circular dichroism of four homogeneous preparations of ATPase (adenosine triphosphatase) from Micrococcus lysodeikticus differing in molecular structure and enzymic properties were examined at pH 7.5 and 25 degrees. Emission was maximum at 325 and 335 nm and the relative intensities at these wavelengths may be used to characterize the different ATPase preparations. The circular-dichroism spectra exhibited negative extrema at 208 and 220 nm, and the relative value of the molar ellipticity at these wavelengths was also different for each molecular form of the enzyme. 2. The four preparations undergo two consecutive major unfolding transitions in guanidinium chloride (midpoints at 0.94 and 1.5 M denaturant), with concomitant destruction of the quaternary structure of the protein. A comparatively minor alteration in the ATPase structure also occurred in 0.05-0.2M-guanidine and led to complete inactivation of the enzyme. The inactivation and the first unfolding transition were reversible by dilution of the denaturant; the transition with midpoint at 1.5M-guanidine was irreversible. 3. Similar results were obtained in urea, except that the successive transitions had midpoints at concentrations of denaturant of 0.4, 2.0 and 4.5M. Low concentrations of urea caused a noticeable activation of the enzyme activity and alterations of the electrophoretic mobility of the ATPase. 4. A model is proposed in which one of the major subunits, alpha, is first dissociated and unfolded reversibly by the denaturants, followed by the irreversible unfolding and dissociation of the other major subunit, beta, from subunit delta and/or the components of relative mobility 1.0 in dodecyl sulphate/polyacrylamide-gel electrophoresis (rho).
Adenosine Triphosphatases↗
Isolation and partial characterization of magnesium ion- and calcium ion-dependent adenosine triphosphatase activity from bovine brain microsomal fraction.
Microsomal fraction was prepared by ultracentrifugation of homogenates of cortical tissue from bovine brains. The preparation displayed ATPase (adenosine triphosphatase) activity in the presence of Mg(2+) (6.4mumol of P(i)/h per mg of protein) and Ca(2+) (3.4mumol of P(i)/h per mg of protein). Kinetic analysis of the activation of the enzyme preparation by Ca(2+) resulted in the demonstration of two apparent K(m) values for Ca(2+) (6.0x10(-8)m and 1.2x10(-6)m). Treatment of the microsomal membranes with Triton X-100 resulted in solubilization of the ATPase, though with some loss of activity. The solubilized microsomal proteins were incorporated into liposomes. By incubation of the liposomes in media containing (45)Ca(2+) an ATP-dependent uptake of Ca(2+) was demonstrated. The solubilized preparation was subjected to preparative isoelectric focusing in granulated gel beds. Two distinct peaks of Mg(2+)- and Ca(2+)-dependent ATPase activity were observed at pH4.8 (peak 4.8) and at pH6.3 (peak 6.3). The material isolated in peaks 4.8 and 6.3 was focused in polyacrylamide gel with pH gradients. The material corresponding to peak 4.8 consisted of a single protein, whereas peak 6.3 contained one major and at least one minor protein. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis confirmed these results and indicated that the major component of peak 4.8 and the protein of peak 6.3 both had a molecular weight of 105000. The material in peaks 4.8 and 6.3 was assayed for ATPase activity in the presence of various concentrations of Ca(2+). Kinetic analysis of the results for peak 4.8 demonstrated an apparent K(m) value for Ca(2+) of 4.1x10(-8)m. The enzyme isolated at pH6.3 had an apparent K(m) value of 3.8x10(-6)m. However, when the material from peak 4.8 was incubated in the presence of 1mm-Mg(2+) the ATPase could not be activated by Ca(2+).
Adenosine Triphosphatases↗
Properties and function of the proton-translocating adenosine triphosphatase of Clostridium perfringens.
Growth of Clostridium perfringens was inhibited by compounds which dissipate or prevent the formation of electrochemical proton gradients. Membrane vesicles prepared from this organism exhibited Mg2+-dependent adenosine triphosphatase (ATPase) activity sensitive to N,N'-dicyclohexylcarbodiimide. Mg2+-ATPase activity was optimal of 50 degrees C, but no discrete pH optimum was observed. Adenosine triphosphate-dependent quenching of the fluorescence of the weak base quinacrine by everted membrane vesicles suggested that the Mg2+-ATPase is a proton pump capable of generating an electrochemical proton gradient. Adenosine triphosphate-dependent transport of Ca2+ by everted vesicles was sensitive to uncouplers and inhibitors of the Mg2+-ATPase.
Adenosine Triphosphatases↗
[Adenosine triphosphatase, lactate dehydrogenase and glucose-6-phosphate dehydrogenase activity of pancreas of thyroidectomized rats].
Activity of enzymes catalizing bioenergetic processes of substance transport through cell membranes, adenosine triphosphatase and para-nitrophenyl phosphates, activity of certain enzymes of carbohydrate metabolism, lactate dehydrogenase and glucose-6-phosphate dehydrogenase, as well as to 5'-nucleotidase taking part in nucleic metabolism were determined in the pancreas of thyreoidectomized rats. Simultaneously the content of lactic acid, phosphorus, potassium and sodium, which immediately related to activation of the mentioned enzymes, was determined in the pancreas. In thyroidectomized rats the activity of Mg2+, Na+, K+-ATPase, Na+, K+-ATPase and lactate dehydrogenase in the pancreas increases, that of glucose-6-phosphate dehydrogenase, para-nitrophenylphosphatase and 5-nucleotidase decreases, the content of lactic acid, potassium, sodium and phosphorus increases.
4-Nitrophenylphosphatase↗
Sodium-potassium-activated adenosine triphosphatase of electrophorus electric organ. X. Immunochemical properties of the Lubrol-solubilized enzume and its constituent polypeptides.
Detergent (Lubrol WX)-solubilized sodium-potassium-activated adenosine triphosphatase ((Na+ + K+)-ATPase) of electrophorus electric organ contains two major constituent polypeptides with molecular weights of 96,000 and 58,000 which can be readily demonstrated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. These two polypeptides can be clearly separated and can be obtained in milligram quantities by preparative sodium dodecyl sulfate gel electrophoresis. The separated polypeptides, after removal of sodium dodecyl sulfate, and Lubrol-solubilized (Na+ + K+)-ATPase activity to some degree. Moreover, the degree of inhibition is directly proportional to the increasing amounts of antisera. The inhibition is maximal 4 weeks after the first injection. Immunodiffusion in 1% agar gel indicated that only Lubrol-solubilized enzyme antiserum, but not 58,000-dalton or 96,00-dalton polypeptide antiserum, gives one major precipitin band. However, specific complex formation between each polypeptide antiserum and Lubrol-solubilized enzyme occurs. This was demonstrated indirectly. After incubating Lubrol-solubilized enzyme with increasing amounts of polypeptide antisera at 37 degrees for 15 min, they were placed in the side wells of an immunodiffusion plate with antiserum against Lubrol-solubilized enzyme in the central well. The intensity of the precipitin band decreased with increasing amounts of polypeptide antisera. Thus, the results indicate that both 96,000-dalton and 58,000-dalton polypeptides are integral subunits of (Na+ + K+)-ATPase.
Adenosine Triphosphatases↗
The activation of sodium-plus-potassium ion-dependent adenosine triphosphatase from marine teleost gills by univalent cations.
The apparent affinity constants for the binding of Cs+, Rb+, K+, Li+, Tl+ and NH4+ to (Na+ + K+)-dependent adenosine triphosphatase from teleost gills were measured and the values discussed in terms of the ion-selectivity isotherm described by Eisenman & Krasne (1975) [in MTP International Review of Science: Biochemistry Series One (Fox, C.F., ed.), vol. 2, pp. 27--59, Butterworths University Park Press, Baltimore]. The ion selectivity of the present enzyme is remarkably similar to that from nerve and brain.
Adenosine Triphosphatases↗
ELECTROPHORUS ADENOSINE TRIPHOSPHATASE: SODIUM-ACTIVATED EXCHANGE AFTER N-ETHYLALEIMIDE TREATMENT.
The microsomal fraction from the electric organ of the eel Electrophorus electricus catalyzes the hydrolysis of adenosine triphosphate in the presence of Mg(++), Na(+), and K(+). The same preparation catalyzes a Mg(++)-dependent transphosphorylation between adenosine triphosphate and adenosine diphosphate. Both of these reactions are inhibited after treatment of the microsomes with N-ethyl maleimide. However, the addition of Na(+) reactivates the transphosphorylation, and the rate becomes more rapid than that of the original. This new Na(+)-sensitive exchange reaction is believed to be a component of the hydrolytic reaction.
Adenosine Diphosphate↗