Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The properties of a new membrane perturbing agent, adamantyl sulfate (A-1-S) are described. Lobster sarcoplasmic reticular vesicles (SRV) were used as a test membrane system and the activity of the Ca2+--Mg2+-dependent ATPase in conjunction with spin label data was used to determine the location of A-1-S in the membrane. The results suggest that A-1-S perturbs only the polar region of the SRV and that this causes loss of ATPase function. Thus, ATPase activity requires integrity of the membrane polar region.
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PMID:Localization of the membrane perturber adamantylsulfate in sarcoplasmic reticular vesicles. 14 14

The Mg2+- and Ca2+-stimulated ATPase (bacterial coupling factor) has been investigated in solution with different independent techniques. The molecular weight of the five-subunit enzyme was found to be 345,000 +/- 5,000 by means of light scattering, 350,000 by sedimentation equilibrium experiments, and 358,000 by means of small-angle x-ray scattering. The radius of gyration was found to be 41.9 A, the volume 7.39 x 10(5) A3, and the surface to volume ratio 5.5 x 10(-2) A-1 from small-angle x-ray scattering measurements of the enzyme in solution. The degree of hydration was found to be 0.62 ml of H2O/g of ATPase. The translational diffusion coefficient was determined to be 3.47 x 10(-7) cm2 s-1 by means of inelastic light scattering. The distribution of the scattered intensity near the origin appears to be bimodal, suggesting that the ATPase molecule is composed of spherical parts bound together by a flexible polypeptide chain. The largest dimension of the ATPase in solution is 120.0 A, determined from the pair distribution function.
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PMID:Size and molecular parameters of adenosine triphosphatase from Escherichia coli. 15 80

It is known that two types of high-molecular-mass protease complexes are present in the cytosol of mammalian cells; a 20S latent multicatalytic proteinase named the proteasome, and a large proteolytic complex with an apparent sedimentation coefficient of 26S that catalyzes ATP-dependent breakdown of proteins conjugated with ubiquitin. In this work, we first demonstrated that a low concentration of SDS was required for activation of the latent proteasome, whereas the 26S complex degraded substrates for proteasomes in the absence of SDS. Moreover, the 26S complex was greatly stabilized in the presence of 2 mM ATP and 20% glycerol. Based on these characteristics, we next devised a novel procedure for purification of the 26S proteolytic complexes from human kidney. In this procedure, the proteolytic complexes were precipitated from cytoplasmic extracts by ultracentrifugation for 5 h at 105000 x g, and the large 26S complexes were clearly separated from the 20S proteasomes by molecular-sieve chromatography on a Biogel A-1.5 m column. The 26S enzyme was then purified to apparent homogeneity by successive chromatographies on hydroxyapatite and Q Sepharose, then by glycerol density-gradient centrifugation. Electrophoretic and immunochemical analyses showed that the purified human 26S complex consisted of multiple subunits of proteasomes with molecular masses of 21-31 kDa and 13-15 protein components ranging in molecular mass over 35-110 kDa, which were directly associated with the proteasome. The purified 26S proteolytic complex degraded 125I-labeled lysozyme-ubiquitin conjugates in an ATP-dependent manner. The 26S enzyme also showed high ATPase activity, which was copurified with the complex. Vanadate and hemin strongly inhibited not only ATP cleavage, but also ATP-dependent breakdown of ubiquitinligated proteins, suggesting that the 26S complex hydrolyzes ATP and ubiquitinated proteins by closely linked mechanisms. These findings indicate that the 26S complex consists of a proteasome with proteolytic function and multiple other components including an ATPase that regulates energy-dependent, ubiquitin-mediated protein degradation.
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PMID:Demonstration that a human 26S proteolytic complex consists of a proteasome and multiple associated protein components and hydrolyzes ATP and ubiquitin-ligated proteins by closely linked mechanisms. 131 98

Chromatium vinosum contains a polypeptide that is functionally and structurally similar to the Escherichia coli chaperonin 10. The protein has been purified to homogeneity by sucrose density gradient centrifugation followed by gel filtration using a Bio-Gel A-1.5 m column. The molecular mass of chaperonin 10, as determined by gel filtration or nondenaturing polyacrylamide gel electrophoresis, is 95 kDa. The oligomer is composed of seven or eight subunits. Comparisons of the overall amino acid composition and N-terminal sequences among chaperonin 10 species from C. vinosum and E. coli reflect a high degree of similarity. A physical association between chaperonins 60 and 10 from C. vinosum, in vitro, is supported by three experimental approaches. First, the proteins form a stable binary complex in sucrose density gradients, gel filtration chromatography, and nondenaturing polyacrylamide gel electrophoresis, solely in the presence of ATP and Mg2+. Second, chaperonin 10 from C. vinosum binds, selectively, to a chaperonin 60-coupled Affi-Gel 10 matrix column. Third, a slight molar excess of chaperonin 10 is able to abolish, almost completely, the ATPase in chaperonin 60. The rate for ATPase activity of chaperonin 60 from C. vinosum is enhanced when supplemented with monovalent cations.
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PMID:Purification and characterization of chaperonin 10 from Chromatium vinosum. 134 70

The membrane bound (Na,K)-ATPase prepared from Artemia salina nauplii was solubilized with a zwitterionic detergent, 3[3(cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), and then purified on a Bio-Gel A-1.5 m column in the presence of the detergent. 1) Upon solubilization, both NaCl and KCl protected the enzyme against loss of activity, KCl being more effective than NaCl. 2) Gel filtration of the solubilized enzyme on a Bio-Gel A-1.5 m column in the presence of 5 mM CHAPS resulted in loss of the enzyme activity even when one of the cations was added. Most of the phospholipids in the solubilized enzyme preparation were removed during the gel filtration (delipidation) and 10-25 phospholipids were left on a protomer (alpha beta) of the enzyme irrespective of the cation present during the gel filtration. With the addition of exogenous phospholipids, the activity was restored. The activity of the enzyme delipidated in the presence of KCl was restored to 3-4 times higher than in the case of that delipidated in the presence of NaCl. 3) Relipidation experiments with a fluorescent phospholipid, dansyl phosphatidylethanolamine (Dans-PE), suggested that the enzyme delipidated in the presence of KCl reassociated with phospholipids more firmly than the enzyme delipidated in the presence of NaCl. From these results we concluded that K+ stabilized the (Na,K)-ATPase more effectively than Na+, even when the enzyme was delipidated.
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PMID:Effects of Na+ and K+ on Artemia salina (Na,K)-ATPase solubilized with a zwitterionic detergent, CHAPS. 284 45

In synaptosomal membranes from rat cerebellum, additive responses to adenylate cyclase activity are observed between the beta adrenergic receptors present on the Purkinje cells and the adenosine A-1 receptors or gamma-aminobutyric acid B (GABAB) receptors, which are both associated with the granule cells. In contrast, nonadditive responses are found with the activation of the adenosine A-1 and the GABAB receptors. Because both receptors are mainly associated with the same cell type, the nonadditive response indicates an interaction between the adenosine A-1, GABAB receptors and the adenylate cyclase. The present study suggests that the nonadditivity results from a limited number of adenylate cyclase catalytic units, which both receptor systems share. This conclusion was derived indirectly by showing that 1) a GABAB agonist did not affect the adenosine A-1 recognition site; 2) both receptors additively activated the high-affinity guanosine 5'-triphosphatase, which is believed to reflect the activation of the inhibitory guanine nucleotide unit; and 3) the nonadditivity was still observed after stimulation of adenylate cyclase activity with forskolin.
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PMID:Co-localized adenosine A1 and gamma-aminobutyric acid B (GABAB) receptors of cerebellum may share a common adenylate cyclase catalytic unit. 298 20

We have previously shown that myosin does not have to detach from actin during each cycle of ATP hydrolysis. In the present study, using the A-1 isoenzyme of myosin subfragment 1, we have investigated the nature of the rate-limiting steps in the ATPase cycle. Our results show that, at 15 degrees C, at very low ionic strength, KATPase determined from the double-reciprocal plot of ATPase activity vs. actin concentration is more than 6-fold stronger than KBINDING determined by directly measuring the binding of A-1 myosin subfragment 1 to actin during steady-state ATP hydrolysis. Computer modeling shows that this large difference between KATPase and KBINDING is not compatible with Pi release being the rate-limiting step in the ATPase cycle. If Pi release is not rate limiting, it is possible that the ATP hydrolysis step, itself, is rate limiting. However, this predicts that, at high actin concentration, the value of the initial Pi burst should be close to zero. Therefore, we measured the magnitude of the initial Pi burst in the presence of actin, using both direct measurement and measurement of relative fluorescence magnitude. Our results suggest that the magnitude of the initial Pi burst in the presence of actin is considerably higher than would be expected if the ATP hydrolysis step were the rate-limiting step in the ATPase cycle.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The rate-limiting step in the actomyosin adenosinetriphosphatase cycle. 623 48

The 26 S proteasome complex catalyzing ATP-dependent breakdown of ubiquitin-ligated proteins was purified from spinach leaves to near homogeneity by chromatography on DEAE-cellulose, gel filtration on Biogel A-1.5, and glycerol density gradient centrifugation. The purified enzyme was shown to degrade multi-ubiquitinated, but not unmodified, lysozymes in an ATP-dependent fashion coupled with ATPase activity supplying energy for proteolysis and isopeptidase activity to generate free ubiquitin. By nondenaturing electrophoresis, the purified enzyme was separated into two distinct forms of the 26 S complex, named 26 S alpha and 26 S beta proteasomes, with different electrophoretic mobilities. The 26 S proteasome was found to consist of multiple polypeptides with molecular masses of 23-35 and 39-115 kDa, which were thought to be those of a 20 S proteasome with multicatalytic proteinase activity and an associated regulatory part with ATPase and deubiquitinating activities, respectively. The subunit multiplicity of the spinach 26 S proteasome closely resembled that of rat liver with minor differences in certain components. No sulfhydryl bond was involved in the assembly of this multicomponent polypeptide complex. Electron microscopy showed that the 26 S proteasome complex had a "caterpillar"-like shape, consisting of four central protein layers, assumed to be the 20 S proteasome, with asymmetric V-shaped layers at each end. These structural and functional characteristics of the spinach 26 S proteasome showed marked similarity to those of the mammalian 26 S proteasomes reported recently, suggesting that the 26 S proteasome is widely distributed in eukaryotic cells and is of general importance for catalyzing the soluble energy- and ubiquitin-dependent proteolytic pathway.
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PMID:Purification and characterization of the 26 S proteasome from spinach leaves. 792 95

We studied 56 patients affected by primary hypercholesterolemia treated with placebo for 1 month and with simvastatin (20 mg/day) or pravastatin (20 mg/day) for 6 months during a double-blind clinical trial. At 1-month intervals we determined the following parameters in the serum: total and HDL cholesterol, triglycerides, and apolipoprotein A-1 and B. At the same time intervals we also determined the cholesterol and phospholipid concentration, the Na+/K+ ATPase activity, and the fluidity of erythrocyte membranes. Our results demonstrated the following modifications in the erythrocyte membranes during simvastatin and pravastatin treatments: (1) an initial increase in cholesterol concentration and in cholesterol/phospholipid molar ratio, with a significant decrease only after 4 months; (2) a similar behavior of membrane fluidity, with an initial decrease and an elevation after 4 months; (3) an increase in the Na+/K+ ATPase activity only after 4 months. We hypothesize that simvastatin and pravastatin not only inhibit the hepatic synthesis of cholesterol, but also modify the cholesterol exchange between plasma and the erythrocyte membrane.
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PMID:Effect of hydroxymethylglutaryl-CoA reductase inhibitors on the functional properties of erythrocyte membranes. 826 65

The aim of this study was to evaluate the long-term effects of cyclosporine (CsA) treatment on urinary concentration ability. Rats were treated daily for 4 wk with vehicle (VH; olive oil, 1 ml/kg sc) or CsA (15 mg/kg sc). The influence of CsA on the kidney's ability to concentrate urine was evaluated using functional parameters and expression of aquaporins (AQP1-4) and of urea transporters (UT-A-1-3, and UT-B). Plasma vasopressin levels and the associated signal pathway were evaluated, and the effect of vasopressin infusion on urine concentration was observed in VH- and CsA-treated rats. Toxic effects of CsA on tubular cells in the medulla as well as the cortex were evaluated with aldose reductase (AR), Na-K-ATPase-alpha(1) expression, and by determining the number of terminal transferase-mediated dUTP nick end-labeling (TUNEL)-positive cells. Long-term CsA treatment increased urine volume and fractional excretion of sodium and decreased urine osmolality and free-water reabsorption compared with VH-treated rats. These functional changes were accompanied by decreases in the expression of AQP (1-4) and UT (UT-A2, -A3, and UT-B), although there was no change in AQP2 in the cortex and outer medulla and UT-A1 in the inner medulla (IM). Plasma vasopressin levels were not significantly different between two groups, but infusion of vasopressin restored CsA-induced impairment of urine concentration. cAMP levels and Gsalpha protein expression were significantly reduced in CsA-treated rat kidneys compared with VH-treated rat kidneys. CsA treatment decreased the expression of AR and Na-K-ATPase-alpha(1) and increased the number of TUNEL-positive renal tubular cells in both the cortex and medulla. Moreover, the number of TUNEL-positive cells correlated with AQP2 or UT-A3) expression within the IM. In conclusion, CsA treatment impairs urine-concentrating ability by decreasing AQP and UT expression. Apoptotic cell death within the IM at least partially accounts for the CsA-induced urinary concentration defect.
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PMID:Long-term treatment with cyclosporine decreases aquaporins and urea transporters in the rat kidney. 1487 80


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