Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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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)

Both native and recombined membrane systems from the human erythrocyte membrane and the rabbit sarcoplasmic reticulum have been studied with 31P Nuclear Magnetic Resonance (NMR). We compare intensities of the anisotropic 31P resonance exhibited by these membranes with the intensity expected from the known phospholipid content of the membranous sample. In a recombinant with human erythrocyte glycophorin, a component of the phospholipid is "missing" from the 31P NMR resonance, apparently due to a severe broadening of the resonance of that component. Approximately 29 phospholipid molecules were found immobilized per glycophorin molecule in the membrane, regardless of the phospholipid:protein ratio. Cholesterol may inhibit the immobilization of phospholipids by glycophorin. Recombinants with band three from the human erythrocyte membrane contain an immobilized phospholipid component, analogous to the results with glycophorin. 31P NMR data from the native sarcoplasmic reticulum membrane also revealed an immobilized phospholipid component whose magnitude is independent of temperature between 30 degrees C and 45 degrees C. Extensive papain proteolysis of the membrane completely digests the Ca++ Mg++ ATPase and removes the immobilization of phospholipids noted in the intact membrane. Limited trypsin cleavage, however, does not completely remove the immobilized component; salt reduces the immobilized component.
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PMID:31P nuclear magnetic resonance studies of the phospholipid-protein interface in cell membranes. 612 13

Transverse tubule membranes isolated from rabbit skeletal muscle have high levels of a Ca2+- or Mg2+-ATPase with Km values for Ca-ATP or Mg-ATP in the 0.2 mM range, but do not display detectable levels of ATPase activity activated by micromolar [Ca2+]. The transverse tubule enzyme is less temperature or pH dependent than the Ca2+-ATPase of sarcoplasmic reticulum and hydrolyzes equally well ATP, ITP, UTP, CTP, and GTP. Of several ionic, non-ionic, and zwitterionic detergents tested, only lysolecithin solubilizes the transverse tubule membrane while preserving ATPase activity. After extraction of about 50% of the transverse tubule proteins by solubilization with lysolecithin most of the ATPase activity remains membrane bound, indicating that the Ca2+- or Mg2+-ATPase is an intrinsic membrane enzyme. A second extraction of the remaining transverse tubule proteins with lysolecithin results in solubilization and partial purification of the enzyme. Sedimentation of the Ca2+- or Mg2+-ATPase, partially purified by lysolecithin solubilization, through a continuous sucrose gradient devoid of detergent leads to additional purification, with an overall 3- to 5-fold purification factor. The purified enzyme preparation contains two main protein components of molecular weights 107,000 and 30,000. Cholesterol, which is highly enriched in the transverse tubule membrane, copurifies with the enzyme. Transverse tubule membrane vesicles also display ATP-dependent calcium transport which is not affected by phosphate or oxalate. The possibility that the Ca2+- or Mg2+-ATPase is the enzyme responsible for the Ca2+ transport displayed by isolated transverse tubules is discussed.
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PMID:Characterization of the Ca2+- or Mg2+-ATPase of transverse tubule membranes isolated from rabbit skeletal muscle. 613 74

Cholesterol hemisuccinate has been shown to equilibrate readily with liposomes and with the (Ca2+-Mg2+)-ATPase from sarcoplasmic reticulum and has been used to modify the sterol content of these membranes. Cholesterol hemisuccinate incorporates into dioleoylphosphatidylcholine (DOPC) up to a molar ratio of 3:1 sterol to DOPC. Effects on lipid order as detected by electron spin resonance and fluorescence polarization are comparable to those of cholesterol. Binding constants have been determined, and the uncharged form of the sterol binds more strongly than the anionic form. Binding to DOPC and to the lipid component of the ATPase system is comparable. From use of the fluorescence quenching properties of 1,2-bis(9,10- dibromooleoyl )phosphatidylcholine and dibromocholesterol hemisuccinate, two classes of binding sites on the ATPase have been deduced. At the lipid/protein interface, the binding constant for cholesterol hemisuccinate is considerably less than that for DOPC. At the second set of sites ( nonannular sites), binding occurs with Kd = 0.55 in molar ratio units. The effect of cholesterol hemisuccinate on the activity of the ATPase depends on the phospholipid present in the system: ATPase reconstituted with DOPC is inhibited whereas ATPase reconstituted with dimyristoleoylphosphatidylcholine is activated. We conclude that changes in membrane fluidity are not important in determining ATPase activity in these systems.
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PMID:Interactions of cholesterol hemisuccinate with phospholipids and (Ca2+-Mg2+)-ATPase. 614 24

The effect of cholesterol incorporation and depletion of the cardiac sarcolemmal sacs on (Ca2+ + Mg2+)-ATPase activity was examined. Cholesterol incorporation to the sarcolemmal sacs was achieved utilizing an in vivo and an in vitro procedure. Cholesterol depleted membranes were obtained in vitro after incubation of the sarcolemmal sacs with inactivated plasma. Arrhenius plots of the (Ca2+ + Mg2+)-ATPase activity showed a triphasic curve when the assays were carried out using a temperature range between 0 and 40 degrees C. The sarcolemmal (Ca2+ + Mg2+)-ATPase activity was shown to be inversely proportional to the cholesterol concentration of the membranes, showing a low ATPase activity with a high cholesterol content and a high ATPase activity when the cholesterol concentration was low. Although the (Ca2+ + Mg2+)-ATPase activity was found to be inhibited in the cholesterol incorporated sarcolemmal sacs, the withdrawal of small amounts of cholesterol from the membranes produced an important stimulatory effect. Changes in (Ca2+ + Mg2+)-ATPase activity due to variation in the membrane cholesterol concentration were shown to be reversible. Our results indicate the possibility of a slow exchange of cholesterol between the tightly bound lipid surrounding the (Ca2+ + Mg2+)-ATPase and the bulk lipid of the sarcolemma.
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PMID:Cholesterol effect on enzyme activity of the sarcolemmal (Ca2+ + Mg2+)-ATPase from cardiac muscle. 614 44

A method is described for reconstruction of certain sarcolemma characteristics of smooth muscle cells in the small intestine of a rabbit on the planar lipid membranes (PLM). The method is based on the use of fusogenic properties of certain lipid preparations. The ultrasound dispergates of azolectin and egg lecithin in combined incubation with sarcolemma vesicles of smooth-muscle cells promote a 1.4-1.8-fold increase of the total ATPase activity of the sarcolemma. Cholesterol, dipalmithoil lecithin, total brain phospholipids, inhibit the ATPase activity. Sarcolemma vesicles preincubated with azolectin lyposomes in the ratio which induces maximum ATPase activation (sarcolemma protein: azolectin-1:6) interact intensively with PLM from azolectin. PLM modified in such a way is channel-conductive, sensitive to tetraethylammonium and sign of the applied voltage.
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PMID:[Reconstruction of the properties of smooth-muscle cell sarcolemma on planar lipid membranes]. 622 19

The cell surface complex (Detering et al., 1977, J. Cell Biol. 75, 899-914) of the sea urchin egg consists of two subcellular organelles: the plasma membrane, containing associated peripheral proteins and the vitelline layer, and the cortical vesicles. We have now developed a method of isolating the plasma membrane from this complex and have undertaken its biochemical characterization. Enzymatic assays of the cell surface complex revealed the presence of a plasma membrane marker enzyme, ouabain-sensitive Na+/K+ ATPase, as well as two cortical granule markers, proteoesterase and ovoperoxidase. After separation from the cortical vesicles and purification on a sucrose gradient, the purified plasma membranes are recovered as large sheets devoid of cortical vesicles. The purified plasma membranes are highly enriched in the Na+/K+ ATPase but contain only very low levels of the proteoesterase and ovoperoxidase. Ultrastructurally, the purified plasma membrane is characterized as large sheets containing a "fluffy" proteinaceous layer on the external surface, which probably represent peripheral proteins, including remnants of the vitelline layer. Extraction of these membranes with Kl removes these peripheral proteins and causes the membrane sheets to vesiculate. Polyacrylamide gel electrophoresis of the cell surface complex, plasma membranes, and Kl-extracted membranes indicates that the plasma membrane contains five to six major proteins species, as well as a large number of minor species, that are not extractable with Kl. The vitelline layer and other peripheral membrane components account for a large proportion of the membrane-associated protein and are represented by at least six to seven polypeptide components. The phospholipid composition of the Kl-extracted membranes is unique, being very rich in phosphatidylethanolamine and phosphatidylinositol. Cholesterol was found to be a major component of the plasma membrane. Before Kl extraction, the purified plasma membranes retain the same species-specific sperm binding property that is found in the intact egg. This observation indicates that the sperm receptor mechanisms remain functional in the isolated, cortical vesicle-free membrane preparation.
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PMID:Isolation and partial characterization of the plasma membrane of the sea urchin egg. 625 14

A rapid isolation method was developed for plasma membranes from mouse lymphoid cells such as lymph node lymphocytes, thymocytes, radiation-induced thymoma cells and L1210 cells. Lysates of these lymphoid cells were prepared by Dounce homogenization under hypotonic conditions and directly layered on sucrose step density gradients containing 2 mM CaCl2 and 5 mM MgCl2, and centrifuged at 52 000 X g for 1 h. Plasma membrane fractions appeared at the interface between 20 and 42% sucrose in the gradients. The procedure permitted purified membranes from cells to be obtained within 3 h, and the preparations appeared to be uniform by electron microscopy. Specific activities of (Na+ + K+)-ATPase, Mg2+-ATPase and 5'-nucleotidase of the isolated plasma membranes were enriched 23- to 61-fold, 12- to 15-fold and 18- to 34-fold, respectively, in comparison with those of the corresponding cell homogenates. Cholesterol content of the malignant cell membranes was lower than that of the normal membranes and the molar ratio of cholesterol to phospholipid of the malignant cell membranes was also lower than that of the normal membranes. A decreased plasmalogen content was observed in the malignant plasma membranes, together with a higher percentage of phosphatidylethanolamine and a lower percentage of phosphatidylserine. In the normal cell membranes, thymocytes contained a higher percentage of phosphatidylcholine and a lower percentage of sphingomyelin than those of the lymph node lymphocytes. At all temperature ranges (5 to 40 degrees C) the plasma membranes of the malignant cells had lower microviscosity than those of the normal cells.
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PMID:Rapid isolation and lipid characterization of plasma membranes from normal and malignant lymphoid cells of mouse. 731 6

These experiments examined effects of cholesterol oxidation on Ca(2+)+Mg(2+)-ATPase activity, Na(+)+K(+)-ATPase activity, and membrane structure of brain synaptic plasma membranes (SPM). Cholesterol oxidase [E.C.1.1.3.6 from Brevibacterium sp.] was used to oxidize cholesterol. Two cholesterol pools were identified in synaptosomal membranes based on their accessibility to cholesterol oxidase. A rapidly oxidized cholesterol pool was observed with a 1t1/2 of 1.19 +/- 0.09 min and a second pool with a 2t1/2 of 38.30 +/- 4.16 min. Activity of Ca(2+)+Mg(2+)-ATPase was inhibited by low levels of cholesterol oxidation. Ten percent cholesterol oxidation, for example, resulted in approximately 35% percent inhibition of Ca(2+)+Mg(2+)-ATPase activity. After 13% cholesterol oxidation, further inhibition of Ca(2+)+Mg(2+)-ATPase activity was not observed. Activity of Na(+)+K(+)-ATPase was not affected by different levels of cholesterol oxidation (5%-40%). SPM interdigitation was significantly reduced and fluidity was significantly increased by cholesterol oxidation. The relationship observed between SPM interdigitation and Ca(2+)+Mg(2+)-ATPase activity was consistent with studies using model membranes [7]. Brain SPM function and structure were altered by relatively low levels of cholesterol oxidation and is a new approach to understanding cholesterol dynamics and neuronal function. The sensitivity of brain SPM to cholesterol oxidation may be important with respect to the proposed association between oxygen free radicals and certain neurodegenerative diseases.
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PMID:Cholesterol oxidation reduces Ca(2+)+MG (2+)-ATPase activity, interdigitation, and increases fluidity of brain synaptic plasma membranes. 755 42

A membrane fraction enriched with plasma membranes was isolated from rat ileal brush-border cells before and after five-day starvation of the animals. Cholesterol/phospholipid ratio of the standard cell membranes decreased highly significantly (0.42 to 0.18), as did the microviscosity of the membranes determined by polarization of fluorescence (0.187 to 0.142). Concomitantly, the specific activity of Na,K-ATPase in the basolateral membranes significantly increased (59 to 83 mumol ATP hydrolyzed per mg protein per min).
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PMID:Modifications of functional and physico-chemical properties of rat ileal plasma membranes. 762 34

CBL/57 strain db/db mice exhibit type II (noninsulin-dependent) diabetes. The affected mice are markedly hyperinsulinemic, hyperglycemic, and hypercholesterolemic, and their serum K+ levels are decreased. The brains of the diabetic mice are significantly smaller than those of their lean, control littermates, but the protein concentration is normal. The low brain weight is accompanied by a loss of major fatty acid components within the whole brain, nerve endings, and mitochondrial membranes. Cholesterol levels are low in whole brain but are not significantly different from normal in the synaptosomal membranes. The phospholipid concentration is significantly decreased in whole brain homogenates, crude synaptosomal membranes, and crude mitochondrial membranes of the diabetic mice. In addition, the specific activities of membrane-bound synaptosomal acetylcholinesterase, Na+,K(+)-ATPase, and Mg(2+)-ATPase are decreased in crude synaptosomal membranes of the diabetic mice. The specific activities of carnitine palmitoyltransferase I and carnitine acetyltransferase are significantly increased in the crude mitochondrial fraction isolated from the brains of the type II diabetic mice, whereas the specific activity of pyruvate dehydrogenase complex is decreased. The specific activities of two other mitochondrial enzymes--monoamine oxidase B and citrate synthase--and a cytosolic enzyme--lactate dehydrogenase--are unaltered. The ability to synthesize cyclic AMP is markedly decreased in the brains of the diabetic mice. The concentrations of carnitine and of the amino acids, glutamate, aspartate, glutamine, and serine are unaltered, whereas glycine levels are significantly elevated in the brains of the db/db mice. The data suggest that in vivo the brains of the diabetic mice exhibit a decreased capacity for glucose oxidation and increased capacity for fatty acid oxidation. This hypothesis is supported by the finding that cerebral mitochondria isolated from the db/db mice oxidize [1-14C]palmitate to 14CO2 at a rate almost twice that of control mitochondria. The present findings emphasize the potentially serious alteration of brain metabolism in uncontrolled type II diabetes.
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PMID:Lipid metabolism and membrane composition are altered in the brains of type II diabetic mice. 772 1


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