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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)

Purified skeletal muscle myosin (EC 3.6.1.3) has been covalently bound to Sepharose 4B by the cyanogen bromide procedure. The resulting complex, Sepharose-Myosin, possesses adenosine triphosphatase activity and is relatively stable for long periods of time. Under optimal binding conditions, approximately 33% of the specific ATPase activity of the bound myosin is retained. Polyacrylamide gel electrophoresis of polypeptides released from denatured Sepharose-Myosin indicates that 85% of the myosin is attached to the agarose beads through the heavy chains and the remainder through the light chains, in agreement with predictions of binding and release based upon either the lysine contents or molecular weights of themyosin subunits. The adenosine triphosphatase of the immobilized myosin has been investigated under conditions of varying pH, ionic strength, and cation concentration. The ATPase profiles of immobilized myosin are quite similar to those for free myosin, however subtle differences are found. The Sepharose-Myosin ATPase is not as sensitive as myosin to alterations in salt concentration and the apparent KM is approximately two-fold higher than that of myosin. These differences are probably due to chemical modification in the region of the attachment site(s) to the agarose beads and hydration and diffusion limitations imposed by the polymeric agarose matrix.
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PMID:Preparation and characterization of an enzymatically active immobilized derivative of myosin. 0 72

The Mg2+-dependent, K+-stimulated ATPase of microsomes from pig gastric mucosa has been studied in relation to observed active H+ transport into vesicular space. Uptake of fluorescent dyes (acridine orange and 9-aminoacridine) was used to monitor the generated pH gradient. Freeze-fracture electron microscopy showed that the vesicular gastric microsomes have an asymmetric distribution of intramembraneous particles (P-face was particulate; E-face was relatively smooth. Valinomycin stimulated both dye uptake and K+-ATPase (valinomycin-stimulated K+-ATPase); stimulation by valinomycin was due to increased K+ entry to some intravesicular activating site, which in turn depends upon the accompanying anion. Using the valinomycin-stimulated K+-ATPase and H+ accumulation as an index, the sequence for anion permeation was NO-3 greater than Br- greater than Cl- greater than I- greater than acetate approximately isethionate. When permeability to both K+ and H+ was increased (e.g using valinomycin plus a protonophore or nigericin), stimulation of K+-ATPase was much less dependent on the anion and the observed dissipation of the vesicular pH gradient was consistent with an 'uncoupling' of ATP hydrolysis from H+ accumulation. Thiocyanate interacts with valinomycin inhibiting the typical action of the K+ ionophore. But stimulation of ATPase activity was seen by adding 10 mM SCN- to membranes preincubated with valinomycin. From the relative activation of the valinomycin-stimulated K+-ATPase, it appears that SCN- is a very permeant anion which can be placed before NO-3 in the sequence of permeation. Valinomycin-stimulated ATPase and H+ uptake showed similar dependent correlations, including: dependence on [ATP] and [K+], pH optima, temperature activation, and selective inhibition by SH- or NH2-group reagents. These results are consistent with a pump-leak model for the gastric microsomal K+-ATPase which was simulated using Nernst-Planck conditions for passive pathways and simple kinetics for the pump. The pump is a K+/H+ exchange pump requiring K+ at an internal site. Rate of K+ entry would depend on permeability to K+ as well as the counterion, either (1) the anion to accompany K+ or (2) the H+ efflux path as an exchange ion. The former leads to net accumulation of H+ and anion, while the latter results in non-productive stimulation of ATP hydrolysis.
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PMID:Potassium-stimulated ATPase activity and hydrogen transport in gastric microsomal vesicles. 3 10

Three new techniques are described for staining the Langerhans cell in whole mounts of fresh human and guinea pig epidermis. These employ paraphenylenediamine, gold sodium thiomalate and cobalt chloride, respectively, and require appropriate epidermal separation with EDTA, ammonium thiocyanate or sodium bromide. Used in conjunction with a modified adenosine triphosphatase stain, these techniques provide greater capability for observing the Langerhans cell in disease states than can be achieved by any single stain. A combined stain with adenosine triphosphate and gold is also described.
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PMID:New staining techniques for the Langerhans cell. 7 Sep 19

A selective staining of the nucleus of both the cells in an islet (of Langerhans) and the acinar cells could be observed after treatment with bromide-water in an ATPase-medium (calcium-cobalt-method) on a cryostatsection of rat pancreas. Furthermore the behaviour of the other metal ion forming a complex has been tested in place of cobalt salt. As conditioned for the staining reaction the hydrolysis of nucleic acid with oxidation of its base by bromide-water and also the complex formation of Co++ with compounds similar to alloxan, resulted from oxidation were discussed.
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PMID:[The reactive behaviour of the cell nucleus after a pretreatment with a bromide solution and the application of the calcium-cobalt-method for the ATPase evidence (author's transl)]. 7 39

The diazido derivative of ethidium bromide has been synthesized as a potential photoaffinity label and shown to be at least as effective as a mitochondrial mutagen as the parent compound, with a similar mode of action. Exposure of mitochondria of Saccharomyces cerevisiae to the compound, followed by ultraviolet-irradiation, which converts it to the highly reactive dinitrene, results in its specific binding to a single component which has been tentatively identified as the smallest polypeptide (subunit 9) of the membrane-bound ATPase. An analogus reaction is also obtained with the soluble, oligomycin-sensitive ATPase complex but not with the F1-ATPase itself. The reaction with the ATPase complex can also be monitored by fluorescence enhancement and by this attribute, as well as by other criteria, diazido-ethidium bromide, ethidium bromide itself, euflavine, N,N'-dicyclohexylcarbodiimide, 2,4-dinitrophenol, and 2-azido-4-nitrophenol all appear to compete for the same, lipophilic, binding site. A mitochondrial mutation (73/1) (see Flury, U., Feldman, F., and Mahler, H.R. (1974) J. Biol. Chem. 249, 6630-6637) produces a photoaffinity product with an altered electrophoretic mobility and molecular weight.
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PMID:Use of diazido ethidium bromide as a specific probe for mitochondrial functions. 12 40

Sarcoplasmic reticulum (Ca2+ + Mg2+)-ATPase was previously shown to have Ca2+-dependent and -selective ionophoric activity when tested in oxidized cholesterol lipid bilayer membranes (Shamoo, A. E., and MacLennan, D. H. (1974) Proc. Natl. Acad. Sci. U. S. A. 71, 3522). ruthenium red, a known inhibitor of (Ca2+ + Mg2+)-ATPase, is found to inhibit the Ca2+-ionophoric activity associated with (Ca2+ + Mg2+)-ATPase. Furthermore, ruthenium red alone acts as an anion-selective ionophore in lipid bilayers with the the following selectivity sequence for anions: l- greater than Cl-, Br- greater than F- greater than NO3-. The PCl-/PNa+ ratio was approximately 4/l. The presence of ruthenium red in excess of Ca2+ ionophore in lipid bilayer experiments converts the cation selectivity of the bilayer due to Ca2+ ionophore into anion selectivity.
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PMID:Mechanism of action of "ruthenium red" compounds on Ca2+ ionophore from sarcoplasmic reticulum (Ca2+ + Mg2+)- adenosine triphosphatase and lipid bilayer. 12 43

Ethidium bromide, in addition to combination with mitochondrial nucleic acids, is a phosphorylation inhibitor during glutamate and succinate respiration by mitochondria. Exhaustive washing of ethidium bromide-treated mitochondria did not relieve the inhibition nor significantly decrease the amount of bound dye. Dialysis against a cation exchange resin at 3 degrees for 17 hr removed about 97% of bound dye. This restored phosphorylating capacity to that of untreated mitochondria which had also been dialyzed against the resin. Since state 3 respiration was diminished and state 4 was unaffected by the presence of the acridine dye, and since neither swelling of mitochondria nor release of latent ATPase was observed, then ethidium bromide was not an electron transport inhibitor nor an uncoupler of oxidative phosphorylation. Inhibition of metabolic processes by ethidium bromide may be due in part to depressed generation of mitochondrial ATP.
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PMID:Ethidium bromide inhibits mitochondrial phosphorylating oxidation. 12 52

HCO3--sensitive ATPase was found in nuclear and plasma membrane fractions of Ehrlich ascites tumour cells and lymphoma NK cells. HCO3--ATPase was not sensitive to monovalent cations and to ouabain (10(-4) M). The 60 mM HCO3- is the concentration of maximal activation of the HCO3--sensitive ATPase. The HCO3--sensitive ATPase was inhibited by anions in the sequence: SCN- greater than F- greater than ClO4- greater J-. The anions Br-, NO3-, HSO3- were not effective.
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PMID:[HCO3-sensitive adenosinetriphosphatase from ascites tumour cells]. 12 89

The (Ca2+ + Mg2+)-dependent ATPase of sarcoplasmic reticulum has been shown to ast as a Ca2+-dependent and selective ionophore in artificial lipid bilayers. Four fragments of 55,000, 45,000, 30,000, and 20,000 daltons have been purified from tryptic digests of the enzyme and it has been shown that the 55,000- and 45,000-dalton fragments are obtained from a single cleavage of the 100,000-dalton ATPase, while the 30,000- and 20,000-dalton fragments are obtained subsequently by a cleavage of the 55,000-dalton fragment. The 55,000- and 20,000-dalton fragments have ionophore activity inhibited by ruthenium red and by mercuric chloride but not by methylmercuric chloride, an inhibitor of the hydrolytic site of the enzyme. Under standard conditions the 45,000-dalton fragment was not active as an ionophore, while the 30,000-dalton fragment acted as a nonselective ionophore. The 55,000- and 30,000-dalton fragments have been shown to contain the site of phosphorylation and of N-ethyl [2-3H]-maleimide binding indicative of the hydrolytic site in the enzyme, and this site is absent from the 20,000-dalton fragment. Therefore, the ionophoric and hydrolytic sites are localized in separate regions of the ATPase molecule and they have now been physically separated. The 20,000-dalton fragment was degraded with cyanogen bromide and fragments were separated by molecular sieving. Ionophore activity was found in fragments of molecular mass less than 2,000 daltons.
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PMID:Localization of ionophore activity in a 20,000-dalton fragment of the adenosine triphosphatase of Sarcoplasmic reticulum. 13 45

Some physiological properties of a multiple-drug-resistant mutant with a permeability barrier to chloramphenicol and its isogenic parental strain were compared. The ATPase specific activity of plasma and mitochondrial membranes isolated from the mutant strain was approximately 20% lower (P less than 0.001, Tables 1 and 2) than that of membranes isolated from the isogenic parental strain. Additional evidence of altered mitochondrial function was: (i) the enhanced growth of the parental strain was eliminted by the [rho-] state (Table 3); (ii) the mutant strain had a greater resistance to petite induction by ethidium bromide (Table 4); (iii) the mutant strain was unable to use a nonfermentable energy source for respiratory adaptation (Table 5). It is proposed that a single gene mutation has resulted in an alteration of some physiological properties of the plasma and mitochondrial membranes.
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PMID:Single gene alteration of plasma and mitochondrial membrane function in Saccharomyces cerevisiae. 14 Oct 2


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