Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A method was developed to isolate renal basolateral membranes from cortical kidney tubule cells of single rats. The isolated membrane fraction was characterized by the measurement of marker enzyme activities and by electron microscopy. 1. After centrifugation of crude plasma membranes on a discontinuous sucrose density gradient the basolateral membranes accumulated at a sucrose density of p= 1.14-1.15 g/ml. The yield was 147 mug membrane protein/g kidney wet weight. Protein recovery was 0.1%. 2. (Na+ + K+)-ATPase was enriched 22-fold from the homogenate. The recovery was 2.6%. The (Na+ + K+)/Mg2+-ATPase ratio was 4.1. 3. The contamination by brush borders was small. Alkaline phosphatase was 1.6-fold enriched and 0.2% was recovered. Aminopeptidase was 1-fold enriched with a recovery of 0.1%. The contamination by mitochondria, lysosomes and endoplasmic reticulum was negligible. 4. In electron micrographs the basolateral membranes showed a typical triple layered profile and were characterized by the presence of junctional complexes, gap junctions or tight junctions.
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PMID:Isolation of the basal and lateral plasma membranes of rat kidney tubule cells. 13 91

Spontaneously hypertensive rats (SHR) and two strains of normotensive rats were compared with respect to enzymatic activities and calcium accumulation of plasma membrane and endoplasmic reticulum enriched fractions from their mesenteric arteries. Increased specific activities of alkaline phosphatase, 5'-nucleotidase and Mg2+-ATPase, and increased ATP-dependent calcium accumulation were found in 5- to 6-month-old SHR as compared to both strains fo age-matched normotensive rats. Alkaline phosphatase was increased in 33-day-old "early hypertensive" and 3- to 4-month-old SHR, but 5'-nucleotidase, Mg2+-ATPase, and calcium accumulation were not. Hydralazine treatment of young SHR partially prevented the increase of both alkaline phosphatase activity and blood pressure that develops with age. The relationship between alkaline phosphatase activity and the alterations in vascular reactivity associated with hypertension remains to be determined.
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PMID:Relationship between blood pressure of spontaneously hypertensive rats and alterations in membrane properties of mesenteric arteries. 13 88

Nuclei, nuclear membranes and rough endoplasmic reticulum (rER) were isolated from onion root tips and stems. Structural preservation and purity of the fractions was determined by electron microscopic and biochemical methods. Gross compositional data (protein, phospholipid, nonpolar lipids, sterols, RNA, DNA), phospholipid and fatty acid patterns, enzyme activities (ATPases, ADPase, IDPase, glucose-6-phosphatase, 5'-nucleotidase, acid phosphatase, and NADH- and NADPH-cytochrome C reductases), and cytochrome contents were determined. A stable, high salt-resistant attachment of some DNA with the nuclear membrane was observed as well as the association of some RNA with high salt-treated nuclear and rER membranes. The phospholipid pattern was identical for both nuclear and rER membranes and showed a predominance of lecithin (about 60%) and phosphatidyl ethanolamine (20-24%). Special care was necessary to minimize lipid degradation by phospholipases during isolations. Nonpolar lipids, mostly sterols and triglycerides, accounted for 35-45% of the membrane lipids. Sterol contents were relatively high in both membrane fractions (molar ratios of sterols to phospholipids ranged from 0.12 to 0.43). Sitosterol accounted for about 80% of the total sterols. Palmitic, oleic, and linoleic acids were the most prevalent acids in membrane-bound lipids as well as in storage lipids and occurred in similar proportions in phospholipids, triglycerides and free fatty acids of the membrane. About 80% of the fatty acids in membrane phospholipids and triglycerides were unsaturated. A cytochrome of the b5 type was characterized in these membranes, but P-450-like cytochromes could not be detected. Both NADH and NADPH-cytochrome c reductases were found in nuclear and rER membranes and appeared to be enriched in rER membranes. Among the phosphatases, Mg2+-ATPase and, to lesser extents, ADPase, IDPase and acid phosphatase activities occurred in the fractions, but significant amounts of monovalent ion-stimulated ATPase, 5'-nucleotidase and glucose-6-phosphatase activities did not. The results obtained emphasize that the close biochemical similarities noted between rER and nuclear membranes of animal cells extend to these fractions from plant cells.
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PMID:Characterization of nuclear membranes and endoplasmic reticulum isolated from plant tissue. 17 22

A procedure for the isolation of plasma membranes from protoplasts of suspension-cultured soybean is described. Protoplasts were prepared by enzymic digestion of the cell wall and the plasma membrane was labelled with radioactive diazotized sulphanilic acid. The membrane systems from broken protoplasts were separated by continuous isopycnic sucrose gradient centrifugation. Radioactivity was localized in a band possessing a buoyant density of 1-14 g ml-1. The activities of NADPH- and NADH-cytochrome c reductase, fumarase, Mg2+-ATPase, IDPase and acid phosphodiesterase in the various regions of the density gradient were determined. A plasma membrane fraction was selected which was relatively uncontaminated with membranes derived from endoplasmic reticulum, tonoplasts and mitochondria. The results indicated that Mg2+-ATPase and possibly acid phosphodiesterase were associated with the plasma membrane.
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PMID:The isolation of plasma membrane from protoplasts of soybean suspension cultures. 56 Oct 89

The aminophospholipid translocase is a plasma membrane Mg2(+)-ATPase which selectively pumps the aminophospholipids (phosphatidylserine and phosphatidylethanolamine) from the outer to the inner monolayer in eukaryotic cells and is predominantly responsible for the asymmetric phospholipid distribution of the plasma membrane. Similar ATP-dependent transport of phospholipid takes place in some organelles such as chromaffin granules. On the other hand, the phospholipid flippase of rat liver endoplasmic reticulum does not require ATP and has a low lipid specificity. The biological implications of these phospholipid flippases are discussed.
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PMID:Control of the transmembrane phospholipid distribution in eukaryotic cells by aminophospholipid translocase. 228 6

Taurocholate transport was characterized in basolateral plasma membrane vesicles prepared from the livers of 14-day-old Sprague-Dawley rats using a self-generating Percoll gradient method. Liver plasma membrane protein yield, intravesicular volume, and enrichments of various marker enzymes were similar to those obtained for vesicles from adult rat liver. The basolateral marker enzyme Na+-K+-ATPase was enriched 26-fold in the suckling rat basolateral membrane fraction while the bile canalicular marker enzymes alkaline phosphatase and Mg2+-ATPase were enriched only 3- and 5-fold, respectively. The activities of marker enzymes for endoplasmic reticulum, mitochondria, or lysosomes were not enriched compared with homogenate. In the presence of an inwardly directed 100 mM Na+ gradient, vesicle accumulation of taurocholate transiently reached a concentration 1.5- to 2-fold higher than that at equilibrium ("overshoot") in suckling and adult membrane vesicles, but the initial rate of taurocholate entry and peak intravesicular accumulation were markedly decreased in suckling compared with adult membrane vesicles. In the presence of an inwardly directed 100 mM K+ gradient, the rate of uptake was slower, and no overshoot occurred in either suckling or adult rat vesicles. The decreased rate of Na+-coupled taurocholate uptake by membrane vesicles from suckling rat liver could not be explained on the basis of more rapid dissipation of the transmembrane Na+ gradient. Kinetic studies demonstrated saturable, Na+-dependent taurocholate uptake for both suckling and adult vesicles. However, the Vmax for taurocholate uptake in suckling rat vesicles was less than half of the adult rate (2.46 +/- 0.13 vs. 5.25 +/- 0.22 nmol X mg prot-1 X min-1, respectively, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Taurocholate transport by basolateral plasma membrane vesicles isolated from developing rat liver. 240 82

It has been shown that the ATP-dependent incorporation of [14C]serine into phosphatidylserine in rat liver mitochondrial and microsomal fractions is prevented by EGTA. On the other hand, at low (microM) Ca2+ concentrations, serine incorporation is strongly stimulated by ATP and Mg2+. This stimulatory effect is reduced by calcium ionophore A23187. It is therefore suggested that the ATP-dependent process is that of serine base-exchange reaction, stimulated by endogenous Ca2+ accumulated inside the microsomal vesicles by Ca2+,Mg2+-ATPase. The mitochondrial activity can be accounted for by contamination by the endoplasmic reticulum.
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PMID:Mechanism of the ATP-dependent phosphatidylserine synthesis in liver subcellular fractions. 253 Jan 9

The cytochemical distribution of Ca2+-Mg2+-ATPase was studied ultrastructurally, using a lead capture method at pH 8.5 and compared in various tissues. In thymic, splenic and activated peripheral blood lymphocytes and in cultured HeLa cells activity was consistently localised on the nuclear envelope, endoplasmic reticulum, Golgi apparatus, mitochondria and weakly on centrioles, but not on the plasma membrane. Intracellular activity was similarly distributed in intestinal absorptive cells where activity was particularly strong in the Golgi apparatus, and in hepatocytes where, however, activity was generally weak. Intracellular activity was lacking in renal glomerular and tubular cells and in cerebellar neurons and neuroglia. Variable activity was present on the outer surface of the plasma membrane, particularly on the brush borders of intestinal and renal tubular absorptive cells, the basolateral invaginations of distal tubules and the bile canaliculi. Mitochondrial activity, when present, was inhibited by oligomycin. The localisation at different sites may represent biochemically different ATPases including endoplasmic reticular ATPase involved in intracellular calcium regulation, oligomycin-sensitive mitochondrial ATPase, dynein-like ATPase associated with centrioles and an ectoenzyme associated with cell surface specialisations.
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PMID:Intracellular distribution of Ca2+-Mg2+ adenosine triphosphatase (ATPase) in various tissues. 253 Jan 99

A monoclonal antibody (mAb 4B4) was raised against purified sarcoplasmic reticulum vesicles from canine myocardium, and shown to inhibit Ca2+ uptake by microsomes isolated from cardiac, skeletal, and smooth muscle. The amount of mAb 4B4 needed to inhibit the Ca2+ uptake 50% at a given membrane concentration correlated with the amount of Ca2+ pump protein in the microsomal preparation. This is consistent with the observation the mAb 4B4 binds specifically to the sarcoplasmic/endoplasmic reticulum Ca2+ pump (Mr 100 kDa), but has no effect on the T-tubule Mg2+-ATPase. Changes in the binding of mAb 4B4 to crude microsomes isolated from dog heart after various durations of global ischemia showed that the decrease in microsomal Ca2+ transport during the first 15 min of ischemia correlated with a loss of active Ca2+ pump molecules. The monoclonal antibody mAb 4B4 may therefore serve as a specific marker for the sarcoplasmic/endoplasmic reticulum Ca2+ pump system in various cells, and can provide quantitative information about the loss of active Ca2+ pump proteins under pathological conditions.
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PMID:Monoclonal antibodies to dog heart sarcoplasmic reticulum as markers of endoplasmic reticulum. 254 29

A membrane fraction enriched in endoplasmic reticulum was prepared from rat parotid glands by using sucrose-gradient centrifugation. The fraction showed a 10-fold increase in specific activity of NADPH: cytochrome c reductase activity over that of tissue homogenates and minimal contamination with plasma membranes or mitochondria. The endoplasmic reticulum fraction possessed both Mg2+ -stimulated ATPase as well as Ca2+, Mg2+-ATPase [( Ca2+ + Mg2+)-stimulated ATPase]activity. The Ca2+, Mg2+-ATPase required 2-5 mM-Mg2+ for optimal activity and was stimulated by submicromolar concentrations of free Ca2+. The Km for free Ca2+ was 0.55 microM and the average Vmax. was 60 nmol/min per mg of protein. The Km for ATP was 0.11 mM. Other nucleotides, such as GTP, CTP or ADP, could not substitute for ATP in supporting the Ca2+-activated nucleotidase activity. Increasing the K+ concentration from 0 to 100 mM caused a 2-fold activation of the Ca2+, Mg2+-ATPase. Trifluoperazine, W7 [N-(6-aminohexyl)-5-chloronaphthalene-1-sulphonamide] and vanadate inhibited the enzyme. The concentration of trifluoperazine and vanadate required for 50% inhibition of the ATPase were 52 microM and 28 microM respectively. Calmodulin, cyclic AMP, cyclic AMP-dependent protein kinase and inositol 1,4,5-trisphosphate had no effect on the ATPase. The properties of the Ca2+, Mg2+ -ATPase were distinct from those of the Mg2+-ATPase, but comparable with those reported for the parotid endoplasmic-reticulum Ca2+-transport system [Kanagasuntheram & Teo (1982) Biochem. J. 208, 789-794]. The results suggest that the Ca2+, Mg2+-ATPase is responsible for driving the ATP-dependent Ca2+ accumulation by this membrane.
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PMID:The (Ca2+ + Mg2+)-stimulated ATPase of the rat parotid endoplasmic reticulum. 294 71


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