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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)

Study of pH-dependence of Ca-ATPase activity of heavy meromyosin (HMM) at low and high ionic strength showed essential differences in the modifying effect of two sulfhydryl reagents, p-CMB and silver. Silver ions in conditions studied independently on pH and KCl concentration produce an inhibition of ATP hydrolysis by myosin and HMM, the shape of the pH-dependence curve remaining similar to that of the native enzyme up to 40% of blocking free sulfhydryl groups. At the same degree of binding of sulfhydryl groups with p-CMB at 0,5 M KCl the pH-dependence curve due to activation at neutral pH changes it's shape and becomes similar to that for dissociation of two ionizable groups (at neutral and alkaline regions). In contrast to this, a low or zero concentrations of KCl no activation was observed for the enzyme with 40-50% of SH-Groups modified by p-CMB and Ca-ATPase in this case seemed to be independent of pH. The data obtained suggest that SH-Groups are not included into the active site of myosin, and the activating effect observed for some sulfhydryl reagents, is due to conformational changes and it can be the result of the penetrance of the organic part of the reagent molecule into hydrophobic region of the protein.
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PMID:[pH-dependence characteristics of Ca-ATPase activity of heavy meromyosin with modified SH-groups]. 1 1

The activation of ATP reversible Pi exchange, normally associated with a Ca2+ concentration gradient in sarcoplasmic reticulum vesicles, can be obtained in "leaky" vesicles in 4-10 mM CaCl2. In the micromolar range, Ag+ activates the ATP reversible Pi exchange two- to fourfold. Similar concentrations of Ag+ promote a parallel inhibition of Ca2+- activated ATP hydrolysis and Ca2+ uptake in intact vesicles. Maximal inhibition of these activities by Ag+ leaves the Mg2+-dependent ATPase unaffected. No net synthesis of ATP was demonstrated in leaky vesicles. The effects of Ag+ depends on the protein concentration and persist after removal of Ag+ from the medium. Membrane phosphorylation from Pi or from ATP is respectively activated or inhibited by Ag+ in reciprocal fashion.
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PMID:ATP reversible Pi exchange and membrane phosphorylation in sarcoplasmic reticulum vesicles: activation by silver in the absence of a Ca2+ concentration gradient. 12 1

Changes were measured in the numbers of chloride cells and the levels of (Na+ + K+)-DEPENDENT ATPase in the gills of immature, yellow eels and mature, silver eels during adaptation from freshwater to seawater. The percentage of chloride cells in yellow eels more than doubled after six days in seawater; at this time the specific activity and concentration of (Na+ + K+)-dependent ATPase in gills start to increase in parallel to reach maxima after two weeks that are 2.5 times the starting values. It is concluded that adaptation of yellow eels to seawater involves an increase in the numbers of chloride cells in gills as well as an increased amount of (Na+ + K+)-dependent ATPase per chloride cell. Mature silver eels in freshwater had essentially the same numbers of chloride cells and the same specific activity of the enzyme in the gills as yellow eels fully adapted to seawater. Transferring silver eels to seawater did not alter the percentage of chloride cells in gills although the level of (Na+ + K+)-dependent ATPase and its specific activity increased slightly. Thus, although the silver eel is better prepared for life in seawater than the yellow eel, it still has to attain an increased level of (Na+ + K+)-dependent ATPase in its chloride cells to be fully adapted to seawater.
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PMID:Changes in the levels of chloride cells and (Na+ + K+)-dependent ATPase in the gills of yellow and silver eels adapting to seawater. 14 Feb 5

Light- and electronmicroscopic and some histochemical investigations on the major excretory ducts of pancreas and liver was carried out on 24 adult chicken. The epithelium of both ducts was shown to include: cells with apical secretory granules, non-differenciated duct cells, ciliated cells and migrating cells. In addition the epithelium of the pancreatic ducts included goblet cells. The distal plasmalemm and the microvilli are covered with surfacecoat, which like the secretory granules produces precipitate with PA-silver. This area of the cell also shows a strong reaction to M++ and Ca++ activated ATPase.
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PMID:[The fine structure of the epithelium of the main outlets from the liver and pancreas of the domestic chicken (author's transl)]. 14 35

The article deals with the influence of sodium dodensylsulfate, lubrol and also of inhibition of Na+,K+-ATPase and Mg2+-ATPase activities by N-ethyl malemid on the form of curves of erythrocyte membranes amperometric titration by Ag+. It is shown that changes in a conformational structure of proteins membranes under the influence of detergents results in the transformation of SH-group of type I to SH-groups of type II. A 70% fall of Na+,K+-ATPase activity has the same result. So, the form of the curves for titration of erythrocyte membranes sulphydryl groups may serve as an indicator to the morpholocial and functional state of the membranes protein part.
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PMID:[Influence of detergents and inhibition of Na+,K+-ATPase and Mg2+ATPase on erythrocyte membrane SH-groups]. 14 2

Glycerol (50%, w/w) was found to cause blistering of chick primary myoblast and fibroblast plasma membranes and extensive blistering of 5--6-day-old-myotube plasma plasma membranes in tissue culture. The tips of myoblasts and fibroblasts appeared to be the most sensitive portion of the plasma membrane to the blistering effect of glycerol. The glycerol-induced blistering of myotubes was reduced and delayed by brief EDTA pretreatment. Glycerol treatment (50, 15 and 8% sequentially) of myotubes was used to remove plasma membrane blisters and a plasma membrane-enriched fraction was isolated from these blisters using a modified Dextran T500-polyethylene-glycol 6000 aqueous two-phase polymer system. This fraction was found to be enriched 4.1-fold for 5'-nucleotidase activity, but not for other putative plasma membrane markers, (Na+ + K+)-ATPase activity or alpha-[125I]bungarotoxin binding material. Autoradiographs of alpha-[125I]bungarotoxin, glycerol-treated (50%, w/w) myotubes showed the plasma membrane blisters to be devoid of reduced silver grains. 5'-Nucleotidase was shown to be an ectoenzyme on myoblasts and 5-day-old myotubes and the total cellular activity was present on the cell surface. During the period of myoblast fusion and myotube formation, cell surface activity decreased to a low level while total cellular activity was elevated.
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PMID:Separation of plasma membrane markers by glycerol-induced blistering of muscle cells. 87 40

Light-and electron-microscopic and some histochemical investigations on the epithelium or the ductus pancreaticus major were carried out in sheep. At least six different cell types are recognizable: (1) nondifferentiated duct cells; (2) cells containing apical secretory granules; (3) goblet cells; the mucosubstances of type 2 and 3 are PAS- and Alcian-blue-positive, also reacting wih methenamine silver; (4) ciliated cells, containing a single cilium with the microtubular pattern 9+2; (5) tuft cells with extremely long and wide microvilli and a pear-shaped cell body; (6) migrating cells, mainly lymphocytes and some assumed eosinophils, showing reaction to Mg++-activated ATPase.
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PMID:[Ultrastructure of the epithelium of the major pancreatic duct in sheep]. 97 Jan 5

By means of silver nitrate impregnation and ATPase methods the distribution of all links of the lymph node vascular bed has been investigated. Structure of the blood capillary wall has been studied electron microscopically; they are defined as capillaries of the I type, that is having a continuous endothelial and basal layers and a small diameter. An essential amount of ribosomes is specific for blood capillary endothelium in the lymph nodes. A dendrite-like ramification of the portal veins is described, dichotomic--for the cerebral arteries, as well as the distribution of cortical arteries and arterioles. The postcapillary venules are found to localize around the lymphoid noduli and in the paracortical zone. Morphological bases for better exchange between blood and lymph are demonstrated in the cortex of the lymph node. Morphological signs of littoral cells of the lymphatic sinuses have been investigated and a conclusion is made on similarity in the structure of the lymphatic sinus wall and the wall of the lymphatic capillaries. Tight structural interrelations have been stated to exist between the wall of the lymph node blood vessels, its stroma and the wall of the lymphatic sinuses.
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PMID:[The morphofunctional characteristics of the vascular bed of the lymph nodes]. 128 89

Ultrastructural localization of Na+, K(+)-ATPase in the exorbital lacrimal gland of rat was investigated quantitatively by protein A-gold technique. Na+, K(+)-ATPase was purified from the rat kidney, and anti-holo Na+, K(+)-ATPase antibody was obtained from the rabbit by injecting the purified enzyme. A specific antibody against the alpha-subunit of Na+, K(+)-ATPase was affinity purified. Immunoblot analysis revealed that the antibody bound specifically to the alpha-subunit of Na+, K(+)-ATPase of the lacrimal gland. Rats were fixed by perfusion with 4% paraformaldehyde containing 1% glutaraldehyde, and the lacrimal glands were embedded in LR White resin. Ultrathin sections were incubated with affinity purified antibody against the alpha-subunit of Na+, K(+)-ATPase, and then with protein A-gold complex. The sections were observed under an electron microscope. Light microscopy with silver enhancement procedure revealed that Na+, K(+)-ATPase was located mainly on the basal region of the cells of intralobular and interlobular ducts. Quantitative immunoelectron microscopic analysis showed that gold particles were found on the basolateral surfaces of the interlobular and intralobular ducts cells and on the basolateral surface of the acinar cells, whereas no significant binding was observed on any part of the apical surfaces of these cells. Labeling density of gold particles was highest on the basolateral surface of the interlobular duct cells, secondarily highest on the basolateral surface of the intralobular duct cells, and lowest on the basolateral surface of the acinar cells. The distribution pattern of Na+, K(+)-ATPase in the acinar cells and the duct cells suggest that this enzyme may play an important role in primary secretion and in determining the composition of electrolytes in the final secretion, respectively.
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PMID:Ultrastructural localization of Na+, K(+)-ATPase in the exorbital lacrimal gland of rat. 130 29

Proteins in human red cell hemolysate were purified to determine which of them increase inhibition of the Na,K-ATPase in the presence of 2 microM free Ca. Samples purified 600,000-fold inhibited the Na,K-ATPase of human red cells in a Ca-dependent manner and stimulated the (Ca+Mg)-ATPase. These samples contained two proteins as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE): calmodulin (18,000 Mr), which comprised most (greater than 90%) of the total protein, and an unidentified protein of approximately 13,000 Mr. Both proteins were a distinctive light yellow when stained with silver. Calmodulin from bovine testes also inhibited the Na,K-ATPase and stimulated the (Ca+Mg)-ATPase. This preparation also contained two proteins as analyzed by SDS-PAGE: calmodulin (95 to 99% of the total protein) and another protein of approximately 13,000 Mr (1 to 5% of the total protein). Both were light yellow when stained with silver. Since the amount of red cell protein was limited, the remainder of the study was carried out with the bovine testes preparation. Heating the testes preparation decreased, but did not abolish, inhibition of the Na,K-ATPase and reduced stimulation of the (Ca+Mg)-ATPase. When corrected for denatured calmodulin, both heated and unheated proteins increased inhibition of the Na,K-ATPase to the same extent. The Na,K-ATPase was inhibited at 2 microM free Ca in a dose-dependent manner over a range of 15 to 100 nM calmodulin. To establish if the inhibition was due to the calmodulin or the 13,000 Mr protein, both were electroeluted after SDS-PAGE. Electroeluted calmodulin stimulated the (Ca+Mg)-ATPase and increased Ca inhibition of the Na,K-ATPase. Electroeluted amounts of the smaller Mr protein slightly stimulated the (Ca+Mg)-ATPase, but had no effect on the Na,K-ATPase. This protein was digested with cyanogen bromide, partially sequenced, and thereby identified as a fragment of calmodulin. We conclude that intact calmodulin increases inhibition of the Na,K-ATPase at 2 microM free Ca. We suggest that calmodulin is part of a mechanism mediating the effects of physiological free Ca on the Na,K-ATPase.
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PMID:Calmodulin increases Ca-dependent inhibition of the Na,K-ATPase in human red blood cells. 131 6


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